prolly after 3 years maybe. piranhas can get huge dude. i dunno if you saw that show on animal planet the other day, but they had some HUGE rbp on that show. i think you might see growth for up to 3 years possibly more. it might slow down, but can still show growth. i haven't even seen mine grow for over a month. prolly been the same sizes for over 2 months now.
WOW thats a long time . But on the same note , cool because my reds are
6 " to 7 " and I guess they are about 7 to 8 months old .
I guess thats about 3/4 Inch a month but they do most of their growing
in the first 4 months .
I agree, three years is when major growth will stop. But saying that, piranhas that were several years old have been reported to still be growing, but very slowly and insignificantly.