For me high nitrate is anything over about 40ppm. I see a lot of guys struggling with high nitrates…50,60,80+. Corals will adapt, but I don’t see a reason to get much higher than 40ppm. Most will say…I’m only feeding 1 cube a day. 2 out of 3 are not being honest about what they really feed. The guy that’s telling the truth doesn’t realize that even though he’s currently feeding only one cube per day, the problem was started months prior. I also agree that Phosphate has to be up in ratio with NO3 for the NO3 to start coming down. Not saying it’s impossible to bring it down without elevating PO4, but it works so much easier. Calcium carbonate surfaces will not bind NO3 like they do PO4. However, all the uneaten food with will settle out all over the system (sand, rock, sump, overflow, pipes, etc.) and will typically leech for weeks or months. At this point it’s time to pull out the bacteria like Waste Away, add more bio media like Siporax, and beef up the CUC. It’s gonna be a slow process, but all is not lost! It can feel that way to some reefers. In some cases it’s best to remove the sandbed or vaccum it really well. Guy’s that are heavy feeder’s might benefit from Carbon Dosing, ATS, or a Denitrator.
In almost 95% of cases Nitrates get elevated by what WE put into the system. That includes fish, coral food, and of course fish food. Some reefers just cannot seem to put down the food. We have to decide if we want a reef tank or a fish tank. It’s a tough decision I know, but I think most would like to have a reef tank. Fish are going to beg 24/7, but that doesn’t always mean they need to be fed. That’s my .02 cents.