amphipods i think???

[justinl]

almost certainly amphipods. They usually look like pillbugs that have been squished in by their sides and are also usually curled up a bit at the back end. Look up isopod and amphipod pictures on the net. No need to control imo.

[Dolf]

The long and the short of it is that they will eat the stuff that you really don't want hanging around your tank anyhow. They provide a source of food to certain fish and some corals and are extremely beneficial. I am setting up a 75 gallon refugium specifically for them (and worms, and decapods, and copepods and... well, all of the critters that I love.) Be happy they are there (the major thing that you don't want that is small and white are flatworms... just do a google image search.) The populations of pods will wax and wane depending on available food.