For my college ecology class we have to put together a terrarium or aquarium. For mine I have an African Dwarf Frog, two Golden mystery snails, and three African cichlids. Before putting them together I cleaned the tank that my professor provided with vinegar like the fish guy told me to and rinsed it out very very well. Yesterday evening I put some fish gravel in the bottom some rocks to hid from the other fish and frog in and some aquatic plants. Everything seemed to be going well last night when I left, however this morning around 10:20 my three fish were dead at the bottom of the tank. Both snails and my frog are alive, and one of the snails was eating one of my fish. I'm not sure what caused the death of my fish. The tank is out in the college greenhouse where it stays fairly warm. Everyone elses fish are still alive so maybe my frog killed the fish? Any ideas?