i have a question bout rbp's

ok my dad wants me to put my rbp in my sisters old tank in the living room and he want me to have more than one can i introduce one to him he is only like 3 in long and a year old do they have to be younger to do this? and it is a 50 gal tank

 

RBP's need to be in groups of at least 3 (preferrably 6 or more). Otherwise they'll just be stressed and hide all the time. That said, 55 gallons is too small for a group. These fish can get around a foot long. I wouldn't put them in anything smaller than about a 100 gallon tank (preferrably 6' x 18").

There is a black piranha which must remain solitary, but they get around 16" wich is quite a bit longer than the 55 is wide so that wouldn't realy work either.

If you like the look of piranhas but don't mind losing the aggression, you could try silver dollars. You could keep about 3 or 4 of them in a 55 with a few other tankmates like tetras or cory cats.

-Chelle