New to the site. Some of you guys have sick fish. Anyway. I just picked up a 20 gallon from a tag sale for $5 bucks. I was wondering if there was a 'monster fish" predator I could keep in there. We have 2 tanks already. A 10 gallon, and a 55 gallon which my 2 year old daugther hleps me with. They are both community setups, so I want to make this one a more agrressive tank. Thanks.