tiny animals in my tank

Question
QUESTION: I have a 65 gallen saltwater tank with aprox. 20 lbs of live rock. No reef as of yet. My fish include 2 true perks, 1 pacific blue tang, 1 fox face rabit fish, 1 goby, 1 cleaner shrimp and 2 snails. Lately when I have been changing the filter in my sump, or cleaning the protien skimmer I have found a lot of little critters that look a little like little shrimp. I don't know where they are coming from or what to do about them if anything. When changing the filter there are probably around 20 or 30 of these critters that I can see. Please help. Thanks.

ANSWER: Hi Jonathan. Congratulations you have a very healthy tank! What you are seeing are basically tiny shrimps that come in on your live rocks and multiply under very good water conditions. These amphipods are part of what makes up the zooplankton of your tank. They feed off of the uneaten food particles and detritus that builds up in your tank and then are consumed by your fish. You do not want to do anything about them. They are beneficial to your aquatic environment and in a way help keep your tank cleaner than it would be with out them!

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QUESTION: Is it possible to bring home a crab in a live rock. I have been seeing a small crab the size of a dime in a hole in the rock. I have yet to see it come out but somtimes it sticks its claw out when I am feeding. Is this strange?

Answer
Are you sure it is a crab? It is very possible to bring home crabs on live rock and I have seen this happen many times. You may want to find out what kind of crab it is if you are planning on putting any corals in your tank in the future. Most crabs are not reef safe and you may want to find a way to get rid of it if possible. After the lights have been out for a while try shining a flashlight in the tank where you saw the claw sticking out. Keep doing this until you get a good look at it and can then try to identify it. I have seen some small crabs come in on live rock that get very large and destructive. The reason I asked if you were sure it was a crab is because it is very common to get a pistol shrimp in on your live rock. It is normal feeding behavior for a pistol shrimp to live in a hole and only put its claw out to feed never coming out to be seen. Crabs are usually less discreet and will show themselves and move more freely about your tank. I have lived with a pistol shrimp in my tank for three years and have never seen more than a claw, Yet I have seen many crab hitchhikers and they always seem to be out and about. Pistol shrimps will make a very loud snapping noise when threatened and you may not notice the sound when they are small. As they get bigger they will surely make their presence known. These shrimps are reef safe and you do not have to worry about them. However if you have a crab it may be something you will want to get rid of at some point.