I am curious if any other small species can coexist with my land hermit crabs inside my 20 gal? Here is a picture of my tank. http://i35.photobucket.com/albums/d153/jennerader/crab09006.jpg Inside are 3 medium sized PP hermit crabs. The substrate is coconut and sand, kept at sand-castle consistency. The temp is always between 70-80 F, and the humidity is 70-85%, providing both fresh and salt water, with a secure screen lid. I already have added home bred woodlice, other then that nothing else is kept inside my tank. Someone has already told me mud skippers but I would need to add a larger salt water pond and remove several things to make it safe. Any other suggestions?