Hi everyone, I have 5 x caribe ( 2x11" 2x12" 1x13" ) 2 x piraya (1x11" 1x10") and 3 x red bellys (3x9") I keep them all together in a 180g tank i,ve had these together for about 2.5 years with no problems, previously to this I had a 13" peruvian rhom tank and a red belly tank I have kept piranhas for about 8 years