In my 125 litres tank is my ctenopoma quite agressive fish....IF tank for ctenopoma is smaller than the agression of this fish will be higher...Yes, I'd be curious to know what size tank the OP has. I had one full grown cteno in my 135 gallon with various other peaceful occupants and added 2 more full grown ctenos with no issues. They all 3 get along fine. But a smaller tank could be a different scenario.
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