So before I get roasted on my first post, let me say that I have kept oscars in a 125 gallon so I know that they enjoy space but i will be building a rack for breeding angel fish and guppies (different sized tanks obviously). I would like to have 3 tanks (40 breeder or 55) for keeping one Oscar in one, a school of 3-5 silver dollars, and the other tank would just be an extra to complete the rack. Now the real question is keeping an Oscar in a 40 breeder vs 55. I have searched the forums and hear both sizes. Bigger footprint on 40 vs more length on 55. So let's hear the pros and cons.