[123]

i have 1 rb 2inch how big of a tank for him

 

[SnowCichlid.]

I dont understand you poll?
... but if your asking what size tank you need for the one RBP then somewheres around 20G will do the trick, they prefer shoals though

 

[MPower]

A 20g will be fine for a single p. But are better off is shoals, but will need a larger tank.

 

[rosecityrhom]

It may be 20 gallons per rb but I don't think that really applies to a single piranha. I've seen a few single piranha's in a 20 gallon and they look miserable. I say give em at least 3 feet to work with from side to side and about 18 inches front to back and a single piranha should be happy.