People claim my tank is overstocked with a Tiger Oscar,pleco,jack dempsey,severum,and a green terror.The way I have my 55 gallon set up though, is enough to make my water pristine.So even if you did set up a 55 gallon with those fishes and have the right set up,you shouldn't be seeing any issues.No I am not going to keep my9 inch Oscar in a 55 gallon forever,with the other fishes.I am upgrading to a 150 gallon tank by March