Since Nano aquariums have become very popular over the past few years, I'll share with you some of my favorite Nano-crustaceans.
Many beginner aquarists tend to focus mainly on fish when adding stock to a new aquarium. I think this is because most people start with freshwater aquariums, and there are not a lot of freshwater aquarium invertebrates. Many Nano aquariums are too small for fish. Even the largest Nano aquarium (25 gallons is still considered a "nano" tank) should only contain a few very small fish. Invertebrates produce less waste than fish, so more of them can fit into a small aquarium. The number and variety of saltwater invertebrates available to hobbyists is staggering. The colors, shapes, and behaviors of these animals rival those of fish. So why not make a marine Nano aquarium invertebrate showcase?
Many of the invertebrates I'm going to write about are cryptic and would rarely be seen in a regular sized aquarium. These are ideal for a small aquarium with some live rock and corals.
Top: Allogalathea elegans Bottom: Galathea inflata
Galatheids, or squat lobsters and porcelain crabs, are some of my favorite nano-inverts. They are among the most peaceful invertebrates and are completely reef safe. They are very small, most reaching only up to 1-1/2" or 2" in size. Unless you find a mated pair, two of the same species shouldn't be kept in the same aquarium; they will fight. Common Squat lobsters can sometimes be found as hitchhikers on live rock or corals and make fine pets. These are usually dull colored, though. Crinoid squat lobsters such as the ones pictured above are becoming more common and can be purchased from Liveaquaria.com's Diver's Den. In the wild these crustaceans are commensal on Crinoid feather stars. They use the sea stars for camouflage and steal their food. Crinoid feather stars are next to impossible to keep in aquariums. Luckily, these Crinoid squat lobsters do not require them for survival. They readily accept frozen foods and adapt well to aquarium life. The Galathea inflata in the bottom photo above has been living in my aquarium since November 2007.
A more rare and unusual crab for the nano aquarium is the Zebra crab, Zebrida adamsii. This crab is very peaceful with its tankmates, and it's almost totally reef safe. It does not harm corals, fish, or other crustaceans. However, this crab is an urchin parasite. In the wild they host on fire urchins Asthenosoma varium, consuming their spines. They can move from one urchin to another and do little harm to the urchins. Unfortunately, they only eat urchin spines and do not accept frozen or prepared foods in captivity. Since fire urchins are highly venomous and rare in our hobby, other urchins can be substituted. Pincushion urchins and longspine urchins are favorites of this crab in captivity. It may be necessary to provide urchins continually every few months, as the health of the urchin will decline over time while the crab hosts on it. To prolong the life of the urchins, provide at least two or three per crab. These crabs are highly territorial, so only one per tank is recommended.
If you plan to keep a fish in your Nano aquarium, I would recommend a shrimp goby. Shrimp gobies form fascinating relationships with pistol shrimps from the genus Alpheus. The pistol shrimp digs a burrow in which both animals live, while the goby provides food and warns the poor-sighted shrimp of danger. Any time the shrimp is outside the burrow, it keeps an antennae on the body of the goby. The goby hovers above, acting as a lookout. If the goby is alarmed, it will warn the shrimp with a flick of its tail and dart into the burrow after the shrimp.
The lovely shrimp in the above photo is an Alpheus ochrostriatus, which pairs with gobies of the genus Amblyeleotris and Ctenogobiops.
Some other interesting shrimps for the Nano aquarium include species from the Periclimenes and Urocaridella genus. These shrimps are almost completely translucent with most species having colorful markings. Periclimenes shrimps are usually commensal on anemones or corals, depending on the species, but do not require them for survival in captivity. Urocaridella shrimps are cleaner shrimps. These peaceful, miniscule shrimps only grow up to 1-1/2" on average and readily accept prepared foods in the aquarium. Periclimenes venustus is my personal favorite in this group. I like to call them the "Hand Jive Shrimp" because of the way they wave their claws. Photo from Teguh Tirtaputra's photostream.
One of the oddest looking shrimps for the Nano aquarium is the Ghost Pipe Shrimp, Leander plumosus. Not much is known about this cryptic species, except that their body shape may be used to mimic pipefish, and that like some pipefish, they may be cleaner animals.
I can not write this post without mentioning the shrimps from the family Gnathophyllidae. This family includes Harlequin shrimps and Bumblebee shrimps. Shrimp from this family typically feed on Echinoderms (sea stars and urchins.)
Harlequin shrimp, Hymenocera elegans and H. picta, are indisputably the most beautiful shrimp that can be kept in an aquarium. They have cream colored bodies with purple, blue, and pink markings and paddle shaped claws. Their diet consists exclusively of starfish, most notably from the genus Linkia. They can be expensive, with pairs being sold for around $80.00. But it's worth it. Harlequin shrimp photo by Sergey Parinov.
A less expensive and easier to keep alternative to the Harlequin shrimp is the Bumblebee shrimp, Gnathophyllum americanum. This is the smallest animal I will write about today. Most only reach about 3/4" in size. They will accept frozen meaty foods like cyclops and mysis. Bumblebee shrimp photo from Underwater Australia.
The last shrimp I'll write about today is the Bongo Shrimp, Phyllognathia ceratophthalmus. They are very rare in the aquarium trade, and not much is know about them and their habits. They are closely related to Harelquin shrimps. They command a pretty high price tag, about $100 for a pair. These would be the ultimate Nano-crustacean for the aquarist who loves rare and unusual beauties. Liveaquaria has an amazing video of one of these shrimp eating a brittle star.
Also check out this Youtube video of a Bongo Shrimp in the wild by N. Akimoto: