It's a 3foot tank and I have silver shark several sucking fish, Tetris, convict which I had to desperate as he was attacking everyone, mollies,angel fish, zebra fins, not many to start as I was concerned of them dying, I do have a heater and just a standard pump, have my pump/filter coming as I was wanting to get the right one. Using sand instead of gravel as I was told was better to use sand for better water quality. Had this tank for about a month now. I dnt have a testing kit and I've been having to change the water twice s week as the fish are dying and losing colour I notice their colour comessage darker once water is changed.