hey so all my fish have red semi-inflamed gills. Other than that they are acting normal. All water parameters are normal and i just can't think of what else it could be... worrying about nothing? or is it some sort of bacterial infection?
Anything that causes gill irritation that can cause that.
High ammonia, nitrites or nitrates, bacterial infections, viral infections, Parasitic infections (like flukes), chemicals getting into the water, pH swings.
Low oxygen can also cause gulping with inflamed looking gills. So how is your water turnover? What is your water temperature and are you for sure it's accurate?
When did it happen? Was a new fish added before it happened? How long have the fish been in there and were they added at the same time? Do you feed feeders?
Any of that can introduce parasites or infections into your tank.
Is 0 ppm nitrate normal ie. is this a planted tank or do you have a DSB running?