Not an expert, so can't help much with your nitrates but it would help to have more details what you have going on.
How big is your tank, how many fish, size of fish, feeding regimen, how much rock/sand, refugium setup, skimmer, filter socks, gfo/biopellets, vodka dosing, water change schedule.
Regarding the noise; what kind of noise is it? What kind of flow generators are you using, what size, and settings? If you are using MP40/MP10 both the wet and dry side will eventually wear out. The dry side can be rebuilt but the wet side you can't rebuilt on the newer QD versions and they don't sell rebuild kits for the older non-QD wet side. Either way if it's the wet side, replacement may be necessary for MP40/10 if the wet side is adjusted correctly and it still makes noise.