im gunan say as long as the tank will hold water full (ive went to buy a tank off cl before and when i asked the guy to fill it it leaked half way up) assuming this is why the guy used it for something other then fish. i would give it a nice cleaning with some chlorine. then when you go to fill with water use some dechlorinator and let it sit for atelast 24 hrs with the water and dechlor in it before adding fish. if this is ur first tank do some homework on the nitrogen cycle and also make sure the fish you plan on are all going to be compatable with eachtoerh and have simular water conditions