I had two five inch red bellies in a 150 gallon tank, but took them out when I put 3 two inch gold piranhas in it. there were two 3 inch bala sharks in the tank, and the red bellies never touched them. but the golds have about nipped the fins off of them. My question is if I can put the two types of piranhas in together without them killing eachother. any help would be great.