nitrates are driving me up the wall

[mike31154]

So other than the nitrate readings being what they are, how is your tank doing? Doesn't sound like you have any major problems other than the nitrate readings themselves driving you up the wall. The diatoms on the sand can be taken care of with an occasional blasting from a turkey baster to put them into suspension. Your skimmer will take care of the rest.

I've had my 75 for about two & a half years now and recall some ups and downs with nitrates. My set up as far as tank & live rock is all from previous owners and there wasn't much of a cycle to speak of on initial set up. Subsequently there was a period of slightly elevated nitrates, then they dropped to 0 only to come back up to about what you're experiencing at about the 1 year mark. No matter what I tried, I couldn't get them down, drove me up the wall. However, none of my livestock appeared to be suffering or stressed, although I didn't have much in the way of corals. Not long after scoring some Chaetomorpha algae (thank you Myka) and adding a VorTech for water movement, the nitrates gradually became undetectable.

I'm too new at this to provide expert advice in this regard, but this has been my experience. Not sure whether it was the Chaeto, additional flow or just the system itself maturing to the point where the biological balance was at the point of taking care of whatever nutrients were causing the elevated nitrates. Might be a combination of a number of factors. Each system is more or less unique, don't let nitrates drive you up the wall. Keep an eye on your livestock and general tank condition, water changes and some macro algae should eventually take care of it.

Other factors noteworthy from my experience:

I feed what many folks would consider generously, I don't like to starve my fish at the expense of a super low nutrient system. I feed frozen, granular as well as flake and any changes I've tried to make in that regard did not appear to impact my nitrate readings significantly;

I now have a few coral specimens, softies and several LPS;

I've only recently changed to using RO/DI from treated tap water and must say, that was a wise move as this has cut down on algae issues;

I have run GFO in a canister filter (I don't have a sump at this time) but it appeared to have nil effect in phosphate readings, these have always been very low in my system. I still run a small amount of carbon in my canister which is otherwise empty;

My skimmer is definitely old school, DIY air stone, counter current but it works well, is quiet and uses little power.

At any rate, I'm confident in saying I have yet to lose any livestock due to elevated Nitrates (when they were elevated), so I'm not sure a reading even up to 20 ppm is all that harmful, other than stressing the system owner. SPS dominated system owners obviously need to aim for better numbers than that. You mention that you do not have a hair algae problem so that's a bonus. I admit that that has been an issue with me in varying degrees. I believe the change to RO/DI will gradually take care of that. Good luck with your system and I wouldn't change too much too fast due to your nitrate readings. Keep an eye on the livestock more than anything as an indicator of system health and give it more time.