O.k. heres the deal. I am getting my Grandma a small tank. How many gallons is sutible ( no more than 20) ? I want to put tropical fish in( goldfish get too big) I know absoloutly nothing about tropical fish!! Can you post some links and sites about tropical fish? I need to know what kinds to get. I need top feeders, middle feeders and bottum feeders. I need to know what filtration and ariration systems to get. I need to know what kind and how many plants to get. I need to know how warm to make it. Anythig else important!!!!! Thanx!