I do actually have a filter in there. It's a fluval 2. It's on the left back side of the tank under the rocksI'm glad I built it right. I did a lot of research and looking at other tanks that other people did before building mine. I'm going to pick up a couple more aquatic plants when I get the fire bellies. The tank is 20 gallons so how many do you think I can house in there? I was thinking maybe 3? Also, i was possibly thinking of buying a few guppies to put in the water part as it's deep enough that they would be ok in there and if the frogs feed on them, I'm ok with that.