I am in the process of building my 500 gallon tank 6x4x3 and am seriously considering a schoal of piranhas for it. At first i thought I would just get 25 or so red bellies and call it a day as I've had a schoal of 12 8" RBP in the past that I enjoyed a lot, but the more I look around I really like the gold spilo's and think a large schoal of say 15-20 would be amazing. Would that be possible in a 500 gallon? Would a lot of dither fish help with the fin nipping early on? Any thoughts or suggestions would be great!