Chemicals as in the water treatment for fish. Need to see what they're called again. As for the size of the tank, he and some others were placed inside as a quick make-shift home when the 10 gallon started leaking everywhere. Then he killed the the fish shortly afterwards and then he got big. We...
I have a yellow african male cichlid, from Walmart. He's a couple of years old and now in a small, two gallon plastic aquarium because the big one sprung a leek. We had other fish but he killed ALL OF THEM. Named Killer for that reason.
Anyway, he has a submersible filter, submersible heater...