cichlid and a pirhana

If the RBp get hungry enough they get crazy, and esp in a group, my uncle had a few on them and after he'd come back after a weekend in the snow they would demolish anything put in the tank, including your hand if it got too close to the top of the water.
 
bucktooth

If you are ever going to put something with a RBP get bucktooth tetras. They apparently go great with them and should be one of the only things that you mix with them.
 
It all depends on the aggressiveness of the actual RBP. They can do fine with an assorted amount of fish but they need the tank space to lessen territorial battles, need to be fed very well and need equally aggressive tankmates....I have seen RBP's kept successfully with Oscars in a 185g, with a common pleco in a very large tank....etc....
 
I should mention that one fish tank I acquired (30 tall) had a piranha in it (before I got it). I don't know anything about the piranha, but it was the cause one of the convicts (still in the tank) to have a missing tail.
 
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