My 2000 gallon tank is leaking and I can't find where it's leaking from. It started leaking around 5 gallons an hour in the middle of the night. The tank is plywood and sealed with fiberglass then pond armor. I am looking for ideas on how to locate the leak without completely draining the tank, but it has to be safe for my fish. She is a 40 pound pacu and I don't really want to remove her from the tank unless it is absolutely the last result. I'm thinking some sort of colored liquid that could show me where the water is escaping from?