Try reducing your feeding schedule, check for accumulation of mum & detrius and siphon out & do a 10% water change for 10 consecutive days to bring down your nitrates. 80ppm in a FO
tank is not critical, but never the less, you should try to bring it down as much as you can. I've found that most hardy fish can survive in high nitrates up to 100ppm and a little bit over in a FO
tank, but you subject them to stress and possibly HLLE
and lateral Line disease.