Bug?

Question
I have a little creature that looks just like a bug, with antennae and feet, about 1/4 inch long, running around on the coral rock that my xenia are attached to. A bug underwater? What is it?

Answer
Hi Star. There are many small buglike creatures that can hitch hike into your tank on live rocks and corals. Most of them are completely harmless and in fact very beneficial to your marine environment. What you are most likely seeing are either small copepods(there are hundreds of these so a definite identification is very difficult without personally seeing it) or some kind of amphipod. Amphipods tend to be a little bigger and there is one species which is extremely common called a Gammaridean amphipod, that can be seen by the hundreds especially after lights out in a saltwater tank. most likely this is what you are seeing. These are not bugs but actually more closely resembling small shrimps. They will readily reproduce in your tank and can be an important source of food for filter feeding invertebrates while in the larval stage and larger specimens will be greedily consumed by your fish!