yeah they are 4-6" right now. I am having a hard time finding ones the same size as mine around here at lfs. The only place I can find them is on the internet. I havent been able to measure them exactly, but when my new tank gets here I plan on buying about 4 or 5 more reds.
Yea do what NJ said about taking them out arranging the tanks and putting them back at the same time. They will all be so stressed with the new surronding they wont notice the new fish. Also new territories will help establish your tank.
Ok, so do you think one or two 3-4" reds would be ok in a 10 gallon for about a month maybe until they get a little bigger? I know that a 10 gallon is WAY small but it wouldnt be for long and the ps arent that big yet.
Are there any other kinds of piranhas you can mix in with red bellies? If not, its okay, a tank full of reds would be awesome anyways.
Oh one more qusetion, how many reds can you put in a 125 gallon comfortably for life?