my oscar are 3 inches, redbelly 2inchs, convicts i might get rid of cause they mate all
the time, pleco 5-6 inches they will be moved into a 55 gallon in about 3 months
then the 4 inch redbelly will go into the 33 gallon
ACDC, I mean this in a kind way and am not trying to trash you.
You may want to do a little more research into piranha's. Other than the pleco, there is not much that will live with a p. reds are not solitary fish, they like to shoal and should be kept at a minimum of 3. To have happy reds the 3 should be in atleast a 55.
Just thought you should know.