ok its a long shot since im pretty sure im getting rays and cichla for a 500g i will be picking up within the month, but how would a 8x4x2 tank be with a lot of piranha? think they would still be skittish in a shoal of 20 or so? what would even be a good number for a tank this size? i have 4 in a 100g right now, but they are just starting to stop being skittish and i dont want another tank full of fish i cant really watch. what do you guys think?