I realize that this thread is pretty old, but for those who are reading forums searching for info...I have a 30g tank with about 6 inches of water and lots of rocks and plants for the toads. I use a Whisper in-tank filter made for 20gal. I have had my 5 fire bellies for about 6 years and put some feeder guppies in the tank with them right from the start. I thought the toads might eat them, but they did not...soabout three months later, I bought 5 fancy guppies (1 male, 4 female) and they have thrived. The feeder guppies died off pretty quickly, so now I have all fancy guppies. They breed like crazy, so now there are close to 40 of them in there at any given time. I have also tried a Mystery Snail, it did well and grew for about a year and a half then died. I didn't notice any signs of illness before it died, not sure how long they live. I put a few Ghost Shrimp in there, but after about a week I haven't seen any. My tank has a lot of little hiding spots, so who knows! I hope this is helpful!![]()