Seahorses, Temperature, and Vibrio

I've been working on this project for nearly a decade now. I posted some rough blogs years ago about this issue on this blog, and also reeftools.com. The article below was originally published in the March/April 2016 Tropical Fish Hobbyist magazine, then hosted on reefs.com in January 2017. There may be changes made to this article in the future; my good friend Tami Weiss, owner of fusedjaw.com, discovered a few months ago some new research on the Syngnathid immune system.

Seahorses and Vibrio

Seahorses have long been thought of as being too sensitive to keep in captivity. The truth is that they are actually quite sturdy and resilient, but they are also susceptible to certain conditions and infections as unique as their anatomy. Knowing how to prevent and treat these conditions can significantly increase the lifespan of captive seahorses. Because of the modern captive seahorse diet of thawed frozen food, combined with outdated myths on proper seahorse care such as tropical temperatures and slow water flow being ideal, Vibrio bacterial infections are now one of the leading causes of captive seahorse death.

Erectus cirri. Photo by Felicia McCaulley.

Vibrio is a genus of opportunistic marine bacteria found in warm waters that commonly infects clams, shellfish, corals, Syngnathids, other fish, and humans. Vibrio cholerae is infamous for causing disease in humans, Vibrio coralliilyticus infects certain stony corals, and many Vibrio spp. infect seahorses, other Syngnathids, and fish. Warmer temperatures increase growth, virulence, and concentration of various infectious Vibrio spp. The preferred temperature range for growth and the temperature at which virulence increases for tropical infectious Vibrio species is strikingly similar.

H. erectus female. Photo by Felicia McCaulley.

What Temperatures Favor the Growth and Virulence of Tropical Infectious Vibrio? When tropical seahorses were first collected for home aquariums, it was assumed that they would thrive at tropical temperatures ranging from the upper 70°Fs to the lower 80°Fs. It is now known that housing seahorses and other Syngnathids at or below 74°F can help prevent tropical Vibrio infections [1].

Phyllopteryx taeniolatus. Photo by Felicia McCaulley.

Decades of research show warm summer temperatures to be the most significant factor affecting the abundance and virulence of tropical Vibrio species which commonly infect seahorses [1] [12] such as Vibrio alginolyticus [2] [3], Vibrio parahaemolyticus [3], and Vibrio harveyi [4]. Like V. cholerae, these species are also responsible for infections in humans. Though there have been no reported cases of V. cholerae infecting seahorses, there have been reports of tropical marine fish in captivity contracting V. cholerae [5]. The optimal temperature for Vibrio cholerae survivability and abundance is between 68°F and 86°F. [6] Related tropical Vibrio coralliilyticus and other infectious strains of Vibrio spp. also favor these same temperature conditions.

H. erectus male. Photo by Felicia McCaulley.


Researchers at the Hollings Marine Laboratory discovered a temperature dependent trait in the bacteria Vibrio coralliilyticus, which may be partially responsible for coral bleaching events. Just like the tropical Vibrio bacterium found in seahorses, Vibrio coralliilyticus does not normally cause disease in healthy Pocillopora damicornis coral specimens at a temperature of 75°F, but becomes pathogenic at higher temperatures. Temperatures above 80°F increases the aggression and severity of the infection. Even healthy tissue struggled to resist infection when temperatures reached 83°F [7].

Macroramphosus scolopax. Photo by Felicia McCaulley.

For over a decade, anecdotes from the seahorse hobbyist community showed a correlation between high temperatures and Vibrio bacterial infections in seahorses kept as pets. In the book Working Notes – A Guide to Seahorse Diseases, pathologist Martin Belli M.D. found that strains of Vibrio samples taken from captive seahorses did not grow well in a lab at temperatures lower than 64°F. Seahorse.org members have long advocated seahorse aquarium temperatures below 75°F because, as Dr. Belli shows, tropical Vibrio is more aggressive and virulent at higher temperatures. [1] How is Vibrio Introduced to Aquariums? Both benign and opportunistic bacteria (such as Vibrio spp.) are present in even the cleanest aquariums, as well as in nature. Dr. Belli found that up to 70% of the seahorses he sampled tested positive for Vibrio, but only about 30% actually died from it. Healthy seahorses testing positive are likely to be asymptomatic carriers [1]. Vibrio can be introduced via any infected or asymptomatic crustacean, shellfish, or fish. It also regularly attaches to copepods, some of which are invisible to the human eye [8]. Vibriois ubiquitous in all brackish and saltwater environments including aquariums, and can be present in live rock, corals, or even a drop of water.

H. erectus female. Photo by Felicia McCaulley.

What Makes Seahorses and Other Syngnathids Vulnerable to Vibrio? Seahorses in the wild only eat living crustaceans. In the past seahorse keepers had to constantly provide expensive live foods, but commercial frozen Mysis shrimp has made it easier and less expensive to feed them. The only drawback to frozen diets is that seahorses and other Syngnathids never evolved the immune system tissues called GALT (gut-associated lymphoid tissues) [9] responsible for protecting them from bacteria on dead food. Foods start to decay immediately upon death and freezing only slows this process. After thawing and introduction to the aquarium the food rapidly collects bacteria. Seahorses can suffer from bacterial infections as a result of eating old or decaying frozen food. Seahorses that are fed a live food diet are more likely to survive in aquariums with higher temperatures than seahorses that are fed frozen foods because the live foods are not decaying.

Erectus fry eating brine shrimp. Photo by Felicia McCaulley.

How can Vibrio Infections be Prevented in Captive Seahorses? Nearly all seahorse experts recommend hobbyists employ an aquarium chiller to keep the temperature at or below 74°F. In nature and aquariums alike, tropical Vibrio spp. become more virulent and aggressive at higher temperatures, while its growth is significantly impeded at temperatures below 68°F.

H. erectus. Photo by Felicia McCaulley.

The most obvious way to prevent illness and bacterial infections of any kind is to keep the aquarium water clean. Regular, adequate water changes can not be avoided in a seahorse aquarium. Keep concentrations of nitrates and dissolved organics as low as possible, as these favor the growth of infectious bacteria and cause stress on the seahorse immune system. Using a UV sterilizer, Protein Skimmer, and strong filter can also help keep the water clean. Contrary to popular belief, seahorses thrive with strong, laminar currents. Low water flow creates dreaded “dead zones” that permit the collection of organics and the growth of bacteria. Scrubbing the surfaces and insides of pipes and equipment regularly can prevent the buildup of bacteria there. A crowded seahorse aquarium makes it more likely the seahorses will come into contact with their Vibrio-laden feces.

H. erectus female with cirri. Photo by Felicia McCaulley.

Quarantining new arrivals and animals showing signs of illness is not an option; it is a necessity. Different species of Syngnathids from various regions of the world may be more or less resistant to tropical Vibrio based on the temperatures of their native environments [1]. Vibrio bacteria can even be transferred between tanks via your hands, fish nets, specimen containers, and feeding syringes. If you plan to mix different species of seahorses or pipefishes together you would be taking a risk, but you can help to minimize potential infections by quarantining your new arrivals for at least 9 weeks. The new seahorses must be eating perfectly and be free from symptoms of disease or injuries before introducing them to the main tank, so quarantine for as long as it takes. An appropriately sized and properly installed UV Sterilizer can help reduce infectious bacteria in the aquarium. There is absolutely no fail-safe way to mix seahorse and/or pipefish species together and ensure they will not succumb to Vibrio infection or other transferable diseases or infections. Risk increases with age, water pollution, decreased immunity, stress, and physical damage.

Doryrhamphus excisus male. Photo by Felicia McCaulley.

Seahorse keepers can help prevent Vibrio colonization of thawed frozen food by placing it in a clean feeding dish, or by keeping the food in constant motion using adequate water flow. Nassarius snails and other scavenging “clean-up crew” animals can help consume uneaten food. If food is leftover after a feeding or feces are present before feeding, simply siphon the food or fecal material out of the aquarium. Thawed food remaining after a feeding should never be left in the aquarium for a seahorse to find and consume later.

H. elongatus male sub tropical. Photo by Felicia McCaulley.

Seahorses coming from sub-tropical or temperate zones may have little to no resistance to Vibrio strains found in tropical waters. This is why it is so important to keep cool-water seahorse species at their recommended captive temperature, and to also avoid keeping them at tropical temperatures even for a short time in the wholesale or retail store holding tanks. Keeping cool-water seahorses with tropical seahorses or other fish, especially those from a different ocean, can expose them to strains of Vibrio to which they have no immunity. When cool-water seahorses are exposed to tropical Vibriostrains the resulting infections are very difficult to treat and may kill in less than a day.

White Erectus female. Photo by Felicia McCaulley.

One species of Vibrio known to infect Syngnathids in captivity that prefers temperatures below 68°F is Vibrio splendidus [10]. A new species of Vibrio discovered in 2010 isolated from wild Hippocampus guttulatus seahorses in the Mediterranean called Vibrio hippocampi has an optimal temperature of 68°F [11]. These and similar species may be responsible for infecting weak or damaged seahorses at these temperatures. Keeping temperatures at the lower end of a temperate seahorse species’ preference can help slow the growth of these cool water Vibrio spp. while they are being treated with antibiotics in a quarantine aquarium.

Temperate H. abdominalis. Photo by Felicia McCaulley.

If a seahorse or pipefish develops white or raw patches of eroded skin, especially on the snout, tail, or a wound, it is likely a Vibrio bacterial infection. Immediate relocation of the seahorse to a bare bottom, sterile 10 gallon hospital/quarantine tank with some plastic hitches and the temperature gradually set to 68°F (or lower depending on the seahorse species’ cold tolerance) can slow the rate of infection. Some over-the-counter antibiotic medications commonly effective against Vibrio are Triple Sulfa, Furan 2, and Neomycin [1]. Veterinarians and professionals treating Vibrio in Syngnathids frequently prescribe Doxycycline, Ceftazidime, Chloramphenicol, Ciprofloxacin, and Enrofloxacin. Azithromycin has not yet been widely used in Syngnathids to treat Vibrio, but is effective against Cholera in humans. These drugs can be more effective than OTC medications against aggressive, resistant strains of Vibrio in Syngnathids when used under the direction of a veterinarian. Seahorse hobbyists are recommended to join a seahorse community such as Seahorse.org or FusedJaw.com where they can receive immediate advice if necessary.

Haliichthys taeniophorus tropical sea dragon. Photo by Felicia McCaulley.

1. Martin Belli MD, Claire Driscoll, Marc Lamont. A Guide to Seahorse Diseases: Working Notes 2nd ed. Aug 2005
2. Sabir M1, Cohen N, Boukhanjer A, Ennaji MM. Occurrence and survival of Vibrio alginolyticus in Tamouda BayCell Mol Biol Oct 2011
3. S. Ulitzur. Vibrio parahaemolyticus and Vibrio alginolyticus: Short generation-time marine bacteria. Microbial Ecology Dec 1974
4. LACHLAN HARRIS,1 * LEIGH OWENS,1 * AND SANDRA SMITH. A Selective and Differential Medium for Vibrio harveyi. APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Sept. 1996
5. Plesník V1, Procházková E. Vibrio cholerae 01 in a fish aquarium. Epidemiol Mikrobiol Imunol. 2006 Feb
6. F L Singleton, R Attwell, S Jangi, and R R Colwell. Effects of temperature and salinity on Vibrio cholerae growth. Appl Environ Microbiol. 1982 Nov; 44(5): 1047–1058
7. Arezue F. B. Boroujerdi, Maria I. Vizcaino, Alexander Meyers, Elizabeth C. Pollock, Sara Lien Huynh, Tracey B. Schock, Pamela J. Morris and Daniel W. Bearden. NMR-Based Microbial Metabolomics and the Temperature-Dependent Coral Pathogen Vibrio coralliilyticus. ACS Publications Oct 2009
8. A Huq, E B Small, P A West, M I Huq, R Rahman, and R R Colwell. Ecological relationships between Vibrio cholerae and planktonic crustacean copepods. Appl Environ Microbiol. Jan 1983
9. Takeshi Matsunaga and Arman Rahman. What brought the adaptive immune system to vertebrates? – The jaw hypothesis and the seahorse. Immunological Reviews December 1998
10. Carolin C. Wendling, Frederico M. Batista, K. Mathias Wegner. Persistence, Seasonal Dynamics and Pathogenic Potential of VibrioCommunities from Pacific Oyster Hemolymph. PLOS One Apr 2014
11. José Luis Balcázar, José Pintado, Miquel Planas. Vibrio hippocampi sp. nov., a new species isolated from wild seahorses (Hippocampus guttulatus). FEMS Microbiology Letters June 2010
12. Kai WANG1, Xin WANG2, Qiang LIN. INTESTINAL MICROBIOTA OF SEAHORSES. World Aquaculture 2015

Temperature Affects Marine Vibrio Bacteria

Vibrio is a genus of marine bacteria found in clams, shellfish, corals, Syngnathids, and Cholera in humans (There are even benign species such as Vibrio Fischeri responsible for bioluminescence in some species of squid and fish). Vibrio cholerae infects humans, Vibrio coralliilyticus infects certain stony corals, and Vibrio spp. infect seahorses and other Syngnathids. The preferred temperature range for growth and the temperature at which virulence increases of each of these three infectious Vibrio species is strikingly similar.

The optimal temperature for Vibrio cholerae survivability and abundance is between 68°F and 86°F. Scientists fear that global warming trends may steadily increase the number of Cholera outbreak cases. It is not surprising that Vibrio coralliilyticus and the Syngnathid-specific strains of Vibrio spp. also favor temperature conditions between 68°F and 86°F.

The Magic Numbers

The recent findings of researchers at the Hollings Marine Laboratory in Charleston, South Carolina reported by CORAL magazine (Jan/Feb 2010) show that infectious strains of Vibrio coralliilyticus linked to coral-bleaching events of small polyp stony corals are temperature dependent. Similar to the Vibrio spp. strains that infect seahorses, Vibrio coralliilyticus does not normally cause disease in healthy coral specimens at a temperature of 75°F, but becomes pathogenic at higher temperatures. Temperatures above 80°F increase the acceleration and severity of the infection.

Not much research has been done on the Syngnathid-specific strains of Vibrio, but for years seahorse aquarists have noticed a correlation between high temperatures and Vibrio bacterial infections in their pets. In the book Working Notes – A Guide to Seahorse Diseases pathologist Martin Belli M.D. writes that strains of Vibrio found to affect seahorses did not grow well in a lab at temperatures lower than 64°F. Seahorse.org members have long advocated seahorse aquarium temperatures no higher than 74°F because Vibrio becomes more aggressive and virulent at higher temperatures. Temperatures in the low 80's seem to increase number of cases, rate of infection, and chance of death.

MORE ON VIBRIO from Felicia's Aquarium Adventures:

http://aquariumadventures.blogspot.com/2010/11/seahorses-and-vibrio.html

http://aquariumadventures.blogspot.com/2010/12/seahorse-tank-keep-it-clean.html

Seahorses and Vibrio

The Vibrio bacteria that infect seahorses and pipefish are temperature dependent. Keeping seahorses in a chilled aquarium can greatly reduce the risk of infection or death by Vibrio bacteria.

Different species of seahorses from different parts of the world may be more or less resistant to Vibrio bacteria based on the temperatures of their native environments. The Atlantic Ocean is warmer than other oceans by about 16°F. Hippocampus erectus, H. zosterae, H. reidi and other seahorse species in the Atlantic may have had to adapt by developing stronger immunity to Vibrio bacteria, as warmer temperatures encourage growth of Vibrio, exposing the seahorses to a higher percentage of Vibrio bacteria in their environment than seahorses in other parts of the world. This may explain why H. erectus seahorses, one of the most common seahorse species in the U.S., have been identified as asymptomatic carriers of Vibrio, and when introduced to other species of seahorses can cause severe Vibrio outbreaks.

a beautiful temperate H. elongatus seahorse

Seahorses coming from sub-tropical or temperate zones may have little to no resistance to Vibrio bacteria, especially those strains found in tropical waters. This is why it is so important to keep cool-water seahorse species at their recommended temperature and not to keep them at tropical temperatures even for a short period. Keeping cool-water seahorses with tropical seahorses, especially those from a different ocean, can expose them to strains of Vibrio to which they have no immunity.

There are steps you can take to prevent Vibrio bacterial infections in your aquarium. Invest in one or two good aquarium chillers. Steadily maintain your main tank temperature between 68°F - 74°F for tropical species. A bare bottom aquarium will help prevent build up of bacteria. Scrub the sides and bottom of the tank. Siphon feces before each feeding, and siphon uneaten food shortly after each feeding. A slightly over sized protein skimmer will help maintain water quality.

It is not recommended to mix together different species of seahorses and/or pipefish. Vibrio bacteria can even be transferred via your hands, fish nets, containers, and feeding syringes. If you plan to mix different species of seahorses or pipefish together, you are taking a risk, but you can help to minimize potential infections by quarantining your new arrivals for at least 6 weeks, preferably several months. The new seahorses must be eating perfectly and be in perfect health before introducing them to the main tank, so quarantine for as long as it takes. A UV Sterilizer could theoretically be used to "inoculate" the new seahorses to your existing seahorses' bacteria and vice versa. There is absolutely no fail-safe way to mix seahorse and/or pipefish species together and ensure they will not succumb to Vibrio infection or other transferable disease or infection.

If your tropical species of seahorse develops white, fuzzy patches of eroded skin, especially on the snout or tail, it is likely a Vibrio bacterial infection. Immediately move the seahorse to a bare bottom, sterile 10 gallon hospital/quarantine tank (or simple, plastic Sterilite storage tub/container) with a couple plastic hitches at a temperature of 68°F. Go to the Seahorse.org Emergency forum and start a thread asking for advice; include answers to these questions. Make sure you have the necessary antibiotic medications on hand such as Triple Sulfa or Furan 2 combined with Neomycin. Aggressive Vibrio infections can spread quickly and kill in as little as 24 hours, so act immediately to resolve the issue.

Seahorse Tank - Keep It Clean!

When I first started raising seahorses I got probably the best piece of advice from Dan U. of seahorsesource.com. Dan told me not to let the seahorse fry eat food that had settled on the bottom of the tank by adjusting the flow to keep the food in constant motion."Dead" food like frozen mysis shrimp start to decay immediately and can collect large amounts of bacteria shortly after hitting the floor of a tank. The theory is that seahorses never evolved the GALT (gut-associated lymphoid tissues) in the gut to be able to eat decaying food and can suffer from bacterial infections as a result of eating frozen food diets combined with improper conditions.

seahorse fry who eat food off the floor are more likely to die before reaching the juvenile stage

"A hypothesis is discussed that the adaptive immune system of vertebrates evolved in the gastrointestinal regions of primitive jawed fish (placoderms) due to increased localized injuries and infections which were inadvertently brought about by the novel jaw structures and the predatory life style...Initial study of the seahorse (Hippocampus) indicates that the gut-associated immune tissues may be absent in this teleost species, suggesting an evolutionary link between the adaptive immune system and the jaw structure or eating habit."

-summary of Jaw Hypothesis and the Seahorse by Matsunaga T., Rahman A.

In the wild seahorses do not eat dead, decaying food; they only eat live food. Seahorses obviously have some sort of immune system but do not have the gut-associated immune tissue that protects from bacteria that naturally settle on decaying matter (frozen mysis shrimp). Both benign and infectious bacteria (such as Vibrio spp.) are always present in even the cleanest aquariums and in nature. Once a piece of frozen mysis shrimp comes into contact with the bottom of the aquarium, bacteria begin to colonize and break it down almost immediately. When a seahorse eats a piece of frozen mysis shrimp that has been sitting on the floor of the tank too long, it may not get sick right away. The bacteria passes through its gut and is present in the feces which may then contaminate the next meal. Any seahorse that eats the resulting feces-contaminated food is at high risk for bacterial infection. This is why it is important to siphon before and after each feeding.

Keep your seahorse tank clean, and keep the temperature below 74°F

It is much easier to keep a bare bottom seahorse tank clean than a reef-style seahorse tank. A pair of seahorses in a very large tank are less likely to come into contact with their feces, and the clean-up crew usually takes care of any uneaten food. The more seahorses in an aquarium, the more important it is to keep it clean. Scrub the floor and walls of the aquarium daily to prevent buildup of organic material settling there. Siphon feces before each feeding, and siphon uneaten frozen foods immediately after feeding. Clean filters and all tubing at least once a month. keep concentrations of nitrates, phosphates, and organics as close to 0 ppm as possible, as these favor the growth of infectious bacteria and cause stress on the seahorse immune system. Using a UV sterilizer, Protein Skimmer, and strong filter can also help keep the water clean. Have enough current and water flow in all areas of the tank so that "dead zones" of little or now flow are not allowed collect organics and grow bacteria.

You can do a lot to prevent bacterial infections in your seahorse aquarium by keeping temperatures lower than 74°F. Vibrio spp. bacteria become more virulent and aggressive at higher temperatures, while significantly slowing growth at temperatures below 68°F. Vibrio bacterial infections are now one of the leading causes of captive seahorse deaths. If Vibrio can be spread through frozen food that sits on the aquarium floor too long, this may be why seahorses who are fed a diet of live foods are more likely to survive in aquariums with higher temperatures than seahorses who are fed frozen foods.



Further reading:

http://www.angelfire.com/ab/rayjay/temperature.html 

Keeping multiple species thread on Seahorse.org (sign in to view topic)

Secrets For Success: Rules You Should Follow To Keep Your Seahorse Aquarium Thriving

 

A friendly seahorse hitched on her favorite human’s hand.

So you’re interested in seahorses? It’s easy to see why!

Seahorses are some of the most interesting and unique fish on the planet. They make great pets and can become quite tame. They know who their humans are and will interact with you in ways other fish can not. They can learn to eat from your hand or even hitch on your fingers. You may find that your favorite pet seahorse greets you each morning with a special dance.

Keeping seahorses is not more difficult than keeping a reef aquarium, it’s just different. If you have reefkeeping experience, you will need to unlearn some of what you know and follow a set of seahorse specific rules.

Rule #1: Buy Captive Bred Only

Do not buy wild caught or net pen raised seahorses. Wild caught and net pen raised (maricultured) seahorses are initially less expensive than captive bred seahorses, but end up being more expensive in the long run. They most often carry pathogens that are expensive to treat and don’t always respond to the over the counter medications available to hobbyists.

Seahorse breeders sometimes purchase wild caught and net pen raised seahorses if the species isn’t available as captive bred. Experts recommend wild caught and net pen seahorses are always treated with a number of medications in a quarantine tank for a minimum of 9 weeks, but their survival rate is still fairly low. They usually won’t eat frozen foods and are already “walking dead” from starvation and handling stress when they arrive at your local fish store. Even if a seahorse is eating frozen food, if it is wild caught or net pen raised, chances are good that it’s carrying pathogens that will make it a ticking time bomb.

Beautiful wild-caught Brazliian H. reidi are tempting, but should be left to the seahorse experts.

Only buy captive bred seahorses raised by a breeder who uses a salt mix or properly sterilized sea water. There are a few reputable breeders here in the United States and Europe. You can order directly from the internet or ask your LFS to order them for you.

Ask other seahorse keepers in online forums or facebook groups which breeders they recommend. You can sometimes find captive bred seahorses at your local fish store. Ask the owner or fish buyer who bred the seahorses. If they don’t know, pass. If the breeder isn’t listed on their invoice, it’s probably net pen raised or wild caught. If they know who the breeder is, they’ll want to advertise that because captive bred seahorses are hardier and more valuable. Some net pen raised seahorses are sold as “tank raised” or “tank bred,” but the breeder isn’t known. In those cases, they’ve likely been raised in the same conditions as net pen raised seahorses and carry the same risks. Always find out who bred the seahorse before purchasing to ensure quality.

an exotic, spiky H. barbouri from SeahorseSource, a breeder in Florida

Captive bred seahorses, especially the US endemic Hippocampus erectus, are quite hardy. Contrary to popular belief, seahorses are not particularly fragile when they’re in good condition. They’re much more tolerant of handling than other fish because of their physical build. These demersal animals spend most of their lives with their tails and bodies wrapped around objects in their environments.

Just like puppies, seahorses should be a certain size and age before going to their new homes. It varies by species, but the common H. erectus should be 4 – 6 months old and at least 3” long before you add it to your aquarium. Seahorses smaller than this may not transition well to a new environment and require 4 or more feedings a day. Mature seahorses are hardier and only need 2 or 3 feedings a day. Most reputable breeders won’t sell their seahorses while they are small and still require many feedings a day.

If you’re buying seahorses from your local fish store or a local breeder, choose active seahorses with full bellies. Caved in sides are a clear indication of starvation and malnutrition or internal parasites. Ask to see the seahorses eat. They should be able to aim for the food accurately and not miss or struggle to suck food into the snout. Look for clear eyes and skin without lesions or swollen areas. It’s normal for seahorses to have a covering of fuzzy algae or Cyanobacteria growing on them.

Young seahorse fry covered in algae

Rule #2: Keep Your Tank Clean

Seahorses are not designed to eat dead food; in the wild they only eat live prey. Seahorses lack the gut associated lymphoid tissue in their digestive tract that helps protect most other fish from bacteria on decaying food. This is why it is very important to only offer very fresh frozen foods. If your frozen mysis is more than a few months old or looks brown instead of white, throw it out. Bacteria like Vibrio and Mycobacterium will quickly colonize decaying organic matter in the aquarium, and seahorses are particularly susceptible to these bacteria. If there is leftover food on the bottom of the tank, make sure to quickly siphon it out within an hour after feeding. It’s also wise to siphon out any feces before feeding to prevent accidental ingestion. You can use a simple hose and bucket or a siphon hose that hooks up to the sink. Use an algae scraper like a Mag Float to clean walls regularly. When you change your filter media, make sure you scrub inside your tubing, pumps, filters as well.

Yellow H. erectus on a red sea star.

Rule #3: Maintain the Right Temperature

Seahorses do best in temperatures a bit lower than reef aquariums. Hippocampus erectus prefer temperatures between 68° F and 74° F. Other tropical species like H. reidi, H. comes, and H. kuda like slightly warmer temperatures between 72° F and 74° F. It is true that wild seahorses can be found at higher temperatures in the wild, but since tropical Vibrio bacteria thrive and become more virulent at temperatures above 74° F, captive seahorses do best at or below 74° F. If you’re keeping sub-tropical or temperate seahorses, ask the breeder or a seahorse expert what the correct temperature is for that species.

This seahorse hitched on a heater and was burned. Sadly, she died soon after despite treatment efforts. Photo credit DesertUSA

If you can not maintain a temperature of 74° F or below in your seahorse aquarium, you can use a fan to blow across the top of the water to bring the temperature down a few degrees. The water will evaporate quickly, so have plenty of fresh water on hand to top off the tank. If you need to bring the temperature down more than a few degrees, an aquarium chiller is recommended. You should choose a chiller that is slightly oversized, as this can increase its efficiency and lifespan. If your air conditioner breaks or your power goes out on a hot summer day, have plenty of frozen water bottles in your freezer that you can float in your seahorse aquarium to help keep the temperature cool.

Some seahorse aquariums won’t need a heater. If your home temperature in the winter is too cool or your home’s temperature unstable, you will need a heater. Never put a regular aquarium heater in the main display where seahorses have access to it. Unlike other fish that swim, seahorses will hitch on the heater. When the heater turns on, it will burn the seahorse which can lead to severe injury, infection, and death. You can keep your heater in a sump filter or the back filtration chamber of your all-in-one Innovative Marine or Red Sea tank, or use an in-line heater so your seahorses can not hitch to it.

H. erectus fry about to eat a live adult brine shrimp

Rule #4: Always Quarantine and Condition

It is strongly recommended to quarantine new seahorses, even if they are captive bred and you trust the breeder and supplier wholeheartedly. Seahorses are most often bred in large, sterile vats with one type of hitch and no sand or rock. When you bring home a new seahorse, chances are they’ve never experienced a typical aquarium environment, and it can take some time for them to get used to it. It’s not uncommon for even captive bred seahorses to stop eating frozen food when they’ve gone through shipping stress and then moved to a new environment. This is why quarantining them in a system that is similar to what they were raised in can increase your chances of keeping them alive. Seahorses are much more likely to eat frozen food in a bare bottom tank than a tank with sand. Condition and observe your new seahorses in the quarantine tank for at least 30 days before moving them to the display. Even if they’re your first seahorses, it’s a good idea to quarantine them so they can gain their strength before moving to the display. This will also allow you to observe them for any possible health issues or pathogens that you don’t want to infect the display tank with.

A simple, dimly lit bare bottom tank with a few hitches and a few pieces of cured live rock make a good quarantine tank. You can use cycled sponge filters or HOB filters. Feed at least twice daily and siphon uneaten food within an hour after feeding. Test the ammonia and pH daily and do water changes as needed.

If you have chosen to purchase wild caught or net pen raised seahorses, quarantine and conditioning is a necessity. The process is much longer, more complex, and involves a minimum 9 week de-worming treatment and frozen food training.

Australian pot-bellied seahorses require very chilly water to thrive.

Rule #5: Give Them Room to Grow

Most people only ever see young seahorses in person at pet shops. H. erectus and H. reidi can reach over 7” in length, some growing larger than an adult’s hand. You may be tempted to buy a smaller tank for young seahorses, but they grow so quickly you’ll need to upgrade to a larger tank within a few months.

erectus and H. reidi need a minimum of 30 gallons per pair, but do better with a 50 gallon or larger. Add 20 gallons for each additional pair. If you overcrowd your tank, you’ll find yourself struggling to maintain the water quality and prevent illness in your seahorses. This will end up costing more money and causing you and your seahorses undue stress.

Appropriately sized all-in-one tanks with open tops are perfect for seahorses. Enclosed all-in-one tanks like the Biocube and Nano Cube tend to run too hot for keeping seahorses. Innovative Marine, Red Sea Max, and Red Sea Reefer style tanks are great options for seahorses. Seahorses prefer at least 24” of vertical height for their elaborate courtship and mating rituals.

It can be tempting for a lot of reefers to put seahorses in their existing aquarium’s sump away from their stinging corals and aggressive fish, but this is not a good idea. Reef temperatures tend to be too high for seahorses, and sumps, just like any filter, collect detritus that can attract bacteria and make your seahorses sick if they come in contact with it. Your skimmer pumps and return pump are a major risk for seahorses inside a sump; if they go through a divider or baffle, their tails can easily be caught and destroyed in these pumps.  Seahorses are messy eaters and will increase the nitrate and phosphate levels in your reef tank. Seahorses and other fish belong in the aquarium, not inside a filter.

If you would like to keep seahorses in an aquarium plumbed into your existing aquarium, keep in mind that the temperature will need to be lowered for the health of the seahorses. You will need to do more frequent water changes to control the nitrates and phosphates resulting from your seahorses’ feeding behavior. Hardy corals may do well in an aquarium shared with seahorses, but corals like SPS that prefer very low nitrates and phosphates and warmer temperatures may not thrive.

a herd of H. reidi enjoying a meal together in a large aquarium

Rule # 6: Proper Filtration and Flow Are Key

It is imperative to have enough flow and filtration in your seahorse aquarium. The advice to keep seahorses in a low flow aquarium is outdated. Years ago the majority of seahorses available were small, weak specimens that couldn’t handle normal flow, and this misconception that seahorses need low flow has persisted. The hardy, robust captive bred specimens available today thrive aquariums with normal flow rates. It’s perfectly acceptable to have ten or even 20 or more times turnover in your seahorse aquarium. What isn’t acceptable is a direct jet of flow or if the seahorses have nowhere to swim, dance, or escape heavy, turbulent flow. A spray bar or circle flow assembly can help you eliminate dead spots in the aquarium while giving your aquarium a gentle but high flow rate.

a beautiful pipefish and seahorse reef at the Shedd Aquarium with high flow

Avoid using powerheads or wavemakers in a seahorse aquarium. Seahorses will hitch to the powerhead grate and can get their tails stuck or severely injured by the impeller. If you have a powerhead, you must use a cover or net like a media bag that fits over the entire powerhead because a seahorse can even get into the front of a powerhead with strong flow. Covers on powerheads can be unsightly and will restrict the flow, but frequent cleanings can help.

The best type of filtration for a seahorse aquarium is a sump (the Red Sea Reefer all-in-ones come with simple to install sump filters). A sump can increase total system volume and has room for protein skimmers, refugiums, and media reactors. If your tank is not “reef ready” or drilled, you can add a hang on the back over flow box along with an aqualifter pump. Choose a sump and an properly sized return pump.

If you decide not to use a sump, choose the largest canister filter or HOB filter you can find. Seahorses require heavy filtration, so you’ll regret buying a filter that is merely adequate. With frequent feedings and waste, Seahorse tanks must have effective mechanical filtration—such as filter socks, sponges or filter floss—to remove particulates from your aquarium water. These mechanical filters need to be cleaned or replaced often to avoid a build-up of nitrates.

A skimmer is a highly recommended piece of equipment for a seahorse tank. It was once believed that rogue skimmer bubbles were responsible for Gas bubble disease and pouch emphysema, but today we know that isn’t true. Skimmers actually prevent these ailments by driving off supersaturated gases and removing organics. (prevent GBD by keeping nitrates and organics low and always match the temperature of your water change water.)

UV sterilizers are another must-have piece of equipment. They won’t entirely eliminate pathogens like Vibrio, Mycobacteria, Uronema, and ciliates, but along with proper tank maintenance, they can reduce these pathogens to levels that are easily handled by the seahorse immune system.

Reactors can be useful in seahorse aquariums that have chronically high nitrate or phosphate levels. NP style bio-pellets in bio-pellet reactors are recommended for seahorses.

Check out our handy Reef Tank Packages section which will help you choose all the right equipment for your size tank.

Rule #7: Watch Your Water Parameters

Seahorses are sensitive to low pH and high ammonia. Low pH can cause them to lose their appetites, and high ammonia can burn their sensitive gills and eyes and kill them rather quickly. They’re tolerant of nitrates, but it is still good practice to keep nitrates below 20 ppm because high organics can cause infectious bacteria to bloom. Seahorses need calcium to maintain their bony plates, so keep your calcium and alkalinity levels stable. Salinity should be stable and measured with a refractometer. Specific gravity can be kept between 1.020 and 1.025.

Young H. kuda on a gorgonia skeleton

Rule #8: Create a Seahorse-Friendly Aquascape

Dry Live Rock is perfect for seahorse tanks because it does not contain pests like Aiptasia anemones which can sting and irritate seahorses. Use a variety of shapes including branching live rock for seahorses to hitch on. Live fancy macroalgae can give your seahorses holdfasts as well as control nitrate levels. You may incorporate artificial decor into your aquascape, but make sure the materials are saltwater safe. Not all aquarium decorations are safe for use in saltwater.

This gorgeous male Bluestripe Pipefish is a challenge for reefkeepers and seahorse experts

Rule #9: Keep New Seahorses in a Species-Specific Tank

It is best to keep young, small or new adult seahorses in species-only tanks until they are mature and conditioned. Turn down the light intensity and flow in the display tank a bit while they are adjusting to their new environment. Once your seahorses have gone through quarantine and conditioning, are eating well and fully mature, and have adjusted to the display tank, you may add safe tank mates to the aquarium.

Hardy, photosynthetic Gorgonians make wonderful tankmates for seahorses

Rule #10: Be Mindful About Coral Compatibility

Seahorses are compatible with most soft corals like Zoanthus, Xenia, Cabbage leathers, Tree corals, Spaghetti Finger Leathers, Gorgonians, and small mushrooms. Compatible LPS are not able to consume a seahorse and do not sting. These include Tubastrea, Scolymia, Acanthastrea, Lobophyllia, Turbinaria, etc. Do not house seahorses with any species of coral that could consume the seahorse like Elephant ear mushrooms or LPS corals with large mouths. Stinging corals are extremely dangerous for seahorses. Never put anemones, Euphyllia, Galaxea, or other stinging corals with your seahorses. It is difficult to keep SPS corals with seahorses. Seahorse aquariums tend to have higher nitrate and phosphate levels than SPS corals prefer, and seahorses tend to irritate the SPS by hitching on them.

Euphyllia spp. like frogspawn, torch, and hammer corals are never safe tank mates for seahorses

Rule #11: Don’t Forget About Fish Compatibility

Most fish are not good seahorse tank mates. Some obvious no-nos are triggerfish, puffers, large angels, sharks, aggressive wrasses, Eels, stinging fish like Lionfish, etc. Some seemingly peaceful fish like blennies and clownfish are also risky. Seahorses are not able to escape or defend themselves against attacks even from small fish. Young clownfish can be suitable tank mates, but once they reach maturity, their aggressive behavior poses a serious threat to seahorses. Always have a backup plan when you’re adding fish to a seahorse aquarium. Some fish can be model tank mates for months or years before viciously attacking a seahorse. Make sure you’re able to remove the offending fish if it becomes a problem. Don’t take unnecessary risks, as they usually end in disaster. Remember that your seahorses are more susceptible to some pathogens than other fish, so quarantine all new fish before introducing them to your seahorses to prevent disease outbreaks.

Fish that are always compatible with conditioned seahorses include tiny gobies like Clown, Trimma, Eviota, and Stonogobiops; Dragonets and Scooters; and small, peaceful gobies like Curious Wormfish and Eel Gobies.

War Paint Gobies are tiny, adorable, and peaceful additions to any seahorse tank

Fish that are usually compatible with large adult seahorses include Royal Gramma Basslets, very small Anthias species, Ecsenius Blennies, small Cardinalfish, Dartfish and Firefish, larger Watchman Gobies, small Jawfish, Flasher Wrasses, Assessors, and small Hoplolatilus Tilefish.

D. pessuliferus, the Yellow Banded Pipefish

Pipefish and related species like Sea Moths are compatible with seahorses in terms of temperament, but remember that these are wild caught relatives of seahorses and can easily transmit pathogens to your captive bred seahorses. Many seahorse keepers opt to keep wild caught pipefish separate from their seahorses. If you choose to take the risk, make certain you are quarantining and de-worming your new pipefish for a minimum of 9 weeks before introducing them to your seahorses. This procedure is well documented online. Also remember that wild caught pipefish are difficult to keep in captivity.

Dragonface Pipefish are one of the few Syngnathids that do well in SPS tanks. They’re often used to control Acropora pest red bugs.

Rule #12: Invert Compatibility Matters, Too!

Most small snails are great tank mates for any seahorse. Nassarius snails will help keep the tank clean by eating leftover food you may have missed while siphoning. Tiny hermit crabs are generally safe, but avoid larger crabs that can pinch and injure your seahorse. Clams and scallops can injure or trap a seahorse. Some sea stars and urchins are predatory, so use caution. Small shrimps like Sexy shrimp will be a snack for most seahorses, but medium shrimp like Peppermint shrimp are good tank mates. Avoid cleaner shrimp that may harass and stress seahorses. Large shrimp or lobsters pose a threat to seahorses. Porcelain crabs and small ornamental squat lobsters are peaceful and compatible with seahorses. Feather dusters and non-toxic filter feeding cucumbers are also safe.

Seahorses learn to recognize their humans and will readily eat Mysis shrimp from your hand

Rule #13: Feed Seahorses a Varied Diet

Mysis shrimp is the best staple diet for seahorses. Spirulina enriched frozen brine shrimp contain high amounts of vitamin E and are recommended as treats a few times a week to prevent vitamin E deficiency and myopathy, but don’t have enough highly unsaturated fatty acids to be the main diet. Copepods are excellent nutritious sources of HUFA, but some adult seahorses may not notice them because of their small size. Experiment with different frozen foods to find out what your seahorses like so you can offer them a varied diet.

Rule #14: Vitamins Can Help Prevent Nutritional Deficiencies

Brightwell Aquatics AminOmega is a great HUFA supplement. It is so concentrated, it can even be used to raise seahorse fry. You can use this product to gutload live adult Artemia, or you can soak frozen food in it. Also adding vitamins to your frozen food will help prevent nutritional deficiencies.

Many seahorse keepers train their seahorses to eat from a feeding dish or large seashell. You can also use a product like the CPR Smart Feeder to target feed slow or picky seahorses. It allows you to place the food close to the seahorse instead of broadcasting it all over the tank to be picked up by the filtration or lost under rocks.

This seahorse appears to be thin and unhealthy. Note the deep indents between trunk rings.

Rule #15: Conservation Status – Don’t Believe The Hype

It is a common misconception that seahorses are endangered. Only one species of seahorse, Hippocampus capensis, the African cape seahorse, is endangered in its natural habitat because of pollution, habitat loss, and freshwater run-off. It is not common in the aquarium trade and no longer available for sale in the United States because of low demand. H. capensis is relatively easy to breed in captivity, but prefers cool water and requires a chiller. A few other species of seahorses live in very deep or remote places, so scientists are unable to assess the health of their population.

Today the aquarium trade has very little impact on numbers of wild seahorses. Most seahorses purchased for pets are now bred in captivity. All seahorses are protected by CITES because populations were in decline due to use in the Traditional Chinese Medicine Trade and the Curio souvenir trade.

Seahorse with a small lesion. Address injuries and infections immediately.

Rule #16: Stock Your Medicine Cabinet

Seahorse keepers are urged to have a “medicine cabinet” for their pets. When seahorses get sick, it happens quickly. Some infections can kill in 24 hours. You probably won’t have time to wait until after work to pick up medicine locally, and waiting a day or two for them to arrive in the mail is very risky. Having these medications on hand at all times will allow you to treat your sick seahorse right away and greatly increase their odds of survival. Make sure to replace them when they pass the expiration date!

Before using these medications on your seahorses, please consult a seahorse expert at Marine Depot, a seahorse group on Facebook, or a seahorse forum. These medications must be used in a quarantine or hospital tank unless otherwise directed. Always wear gloves when handling meds and changing water in your hospital tank.

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Recommended Medications:

Antibiotics

• API Furan 2
• Seachem Kanaplex (kanamycin)
• Neosporin (yes, the human kind. Make sure it has no added ingredients)

Anti parasitic

• Seachem Metroplex (metronidazole)
• API Genereal Cure (metronidazole and praziquantel)
• API Super Ich Cure (malachite green and nitrofurarzone)
• Kordon Rid Ich (malachite green and formalin)

Emergency

• Methylene blue
• Kordon Amquel plus

Unsafe medications for Syngnathids

• Copper
• MelaFix

References

• Fusedjaw.org
• Seahorse.org
• Fishbase.org
• https://reefs.com/magazine/seahorses-and-vibrio/
• Seahorses & Pipefish facebook group