I just called a pet store and tommorrow i am going to buy a black piranha. My question is i am going to put him in my 37 gallon aquarium until i get the 55 in a month. The guy said its fine as the fish is only 4.5 inches right now and i was also wondering how much does a test kit usually go for? Thanks for taking time to answer my questions. And i know this should be on the predatory fish discussion, but no one hardly goes on there.