ANYWAYS,
Arowana Man, I've changed my avi since then, and don't remember which one I had, but it's my solo RBP now.
To say that a fish will only grow to the size of the tank is a bunch of malarky if you're taking care of it properly.
A piranha cannot stop growing because he thinks to himself...well, it's getting a little cramped in here, I think I'll slow down a bit.
HOWEVER, If you never change your water, the ammonia in the water will gradually increase to a point where your fish's body will realease a growth inhibiter, simply because his environment cannot support him if he gets any bigger. Make sense?
Piranha will try to shoal with fish whom aren't even of it's species, this isn't because they tolerate each other, but because they NEED the companionship, and it makes them feel more secure... BUT, they will only be as active as the fish they are shoaling with....
My 4" RBP shoals with a pair of plecos named Lucky and Sheba, and he's not that active. (him or the plecs)
My fiance's 2" shoals with a pair of half inch YOY bluegill (they were properly quarentined) and she's ALL over her tank, and doesn't even try eating them.