Unidentified Amphipod. Picture taken October 2000.
Nikon Coolpix 950 digital camera, Tiffen 10x and 7x close-up lens, full flash

These are the little bugs you commonly see crawling around your rocks at night. Of course they are not really bugs but are small crustaceans. Just about any fish will eat these if they can catch one.

These seem to be very active and social critters in areas protected from predators. The larva from these small crustaceans add significantly to the zooplankton population of the tank.

Unidentified Amphipod. Picture taken October 2000.
Nikon Coolpix 950 digital camera, Tiffen 10x and 7x close-up lens, full flash

This Amphipod is a different species then the one above and is much more difficult to see. I find these critters building little tunnels at the surface of the sand bed. The tunnels tend to have trap doors on them that the Amphipods can open and close as needed.

Identification of Amphipods is a highly specialized area. Often you need to know the geographic location the specimen was collected from if you have any hopes to make a close ID.