Yes, I use a 5 stage RODI and I did a 20% water change 12 days ago but nitrates shouldn't be that high. I have a 44 gallon with 2 turbos, over 10 tonga snails, and a couple of porcelain crabs. As for fish, I have 4 clowns, 1 yellow tail damsel, and 1 firefish. I feed my fish frozen food once per day just enough for them to eat up in under 2 minutes. I ordered some peppermint shrimp, more tongas, and a red sea star to help with clean up which should be arriving today. I think part of the issue is such a limited CUC. I have a 5 staeg HOB filter that I replaced the filter on 2 days ago. I haven't ran a skimmer in a couple years but that hasn't been a huge problem with regular water changes.