I'm not sure. how big do they get at full maturity? that is the length you should base your question on. i know you should try and stick to 1" of fish per gallon. and now you would have 12" of fish in a 15 gallon tank. and that rule also depends on how territorial a fish is and how much they eat and poop. so take all that into consideration. sorry i don't have more specific answer. i don't know enough about the species to tell you for certain.