i bought A whisper 20 gallon filter for my fire bellied toads and newts it filters all tanks , half water half rocks , and ful water it is supposed to filter 20 gallons so i think it will be okay conidering there is only 3 gallons of water in the tank. it sucks up the water, filters it, and water falls it back. please let me know if this is okay, here is a picture of it
http://home.comcast.net/~sam_da_man8...D-1109636.html