fin biting

Hey guys, i need your advice. At the moment i keep in my main Tank 4 Polys. Name Gender Age Size Species A Male ~ 3 Years ~ 11" Polypterus Delhezi B Female ~ 3 Years ~ 11,5" Polypterus Delhezi Marty Male ~ 2,5 Years ~ 12" Polypterus Delhezi Würmchen Male ~ 1,5 Year ~ 12,5"...