bugs

Question
I noticed the other day when giving some shrimp pellets to everyone in our 155 gal salt water tank, that a small beige looking bug came right out (during lights on time)and started nibbling on one. The critter was about the size of the pellet. I told my husband and he said that he had seen several before. Since then, when it's just the purple lights on, I can see a whole lot more of them just smaller. I don't know where they came from. I don't know what they are. I don't know if they're good or bad. I assume they aren't to be desired, so, how do I go about getting rid of them? Thanks

Answer
Hi Beth. Before you do anything drastic to rid your tank of these creatures lets first figure out what they are. There are very few creatures that hitchhike into our tanks on live rock that are undesirable. Most of them are harmless and very beneficial scavengers that will do a good job cleaning up any uneaten food particles before they have a chance to rot and pollute the tank. In order for me to give you a proper identification I must know a little more about your mystery creature. Is it a worm or does it actually look like a bug? Does it have legs? Does it look like a small shrimp? Most likely what you are seeing is some kind of arthropod or isopod. These creatures are larger than copepods and can look a little like bugs in your tank. There is one kind of arthropod that is extremely common in a saltwater tank. These little creatures look a little like small shrimps. They are beige in color and have a crescent shaped body. They usually come out when it is dark but can be seen scurrying about at almost any time of the day. Their size will vary and older specimens will be larger than the youngsters. They will reproduce readily in your tank and are a good source of food for your fish, if they can catch them. They are scavengers that feed on detritus and uneaten food particles and algae and are very beneficial because they reach places to clean up that you and your fish can't. Don't be too hasty in trying to rid your tank of these creatures. A healthy marine system will support the life of many small creatures from bacteria to microscopic copepods to the larger arthropods. The reproduction of most of these creatures not only shows that your tank is healthy but also gives your tank a good diversity that also exists in the ocean.