I have an Oscar and two Jack Dempsey. I've had them for about 5-6 months now. And yes, when I bought them I was unaware of their size, attitude... Basically uneducated. Now I am to the point of selling one or two. So that I don't have a jaws movie in my bedroom! I only have a 55 gallon tank. I must say so far nothing crazy has happened but I do want them to be happy and safe. Any suggestions?