Keeping Acropora corals and other SPS alive in captivity can be a challenge, But you can enlist the help of tiny Commensal Acropora crabs and Pocillopora crabs of the Trapezia and Tetralia genus. These crabs are extremely beneficial to Acropora and other SPS corals. They protect the corals from some predators and keep the coral clean. If your aquarium houses SPS (small polyp stony) corals like Pocillopora or Acropora corals, these crabs should acclimate well and be easy to keep. These tiny crabs are very territorial, so only one should be kept per coral unless they are a mated pair. These tiny crabs can be found as hitchhikers on SPS corals or can be purchased online.
|Trapezia septata lives in Pocillopora|
|Trapezia guttata lives on Seriatopora|
|Tetralia spp. live on Acropora|
"The scientists showed the importance of trapeziid crabs by gently removing crabs from sections of the two species of branching corals on a coastal reef. This resulted in 50 to 80 percent of those corals dying in less than a month. By contrast, all corals with crabs survived...For surviving corals that lacked crabs, growth was slower, tissue bleaching was greater, and sediment load was higher. Laboratory experiments revealed that corals with crabs not only shed substantially more of the sediments deposited on coral surfaces, but also that crabs were most effective at removing grain sizes that were most damaging to coral tissues." - from Tiny Crabs Project
Pocillopora and Acropora Guard crab food is provided entirely their host coral. They are easy to keep in captivity, but must be given an SPS coral to host on.
See more photos and read more about Commensal coral crabs at http://www.chucksaddiction.com/hitchcrabs.html