Reducing Nitrates - nothing seems to be working

[srfndoc]

It seems my tank has always registered high for nitrates (50 or higher, tested with two different tests brands including salifert) and I don't seem to be able to reduce it. The tank is about 120gal of water volume and has been running for about 2.5 years. I have about 100lbs of live rock and a SSB (about 1") of fine argonite sand. I get about a full cup of dark yellow skimmate every other day from my skimmer (MRC MR-2). Here are the rest of my params:

Ammonia - 0
Nitrite - 0
Nitrate - 50+ ppm
Phosphates - .1
PH - 8.1
Salinity - 1.023
Temp 80-83F

I do a monthly 20% water change with RO/ASW and topoff thru out the month with RO water. I tested my RO water and it registers 0 for both phosphates and nitrates and registers 2-3 TDS with my tester. I have a large clump of Chaeto in my sump that is growing like mad under one of those spiral lamps, usually doubling in size every month. I do have some large nitrate generators in the tank (two yellow tangs about 3-4" in length) but the rest of my fish are fairly small (two ocellaris, one greem chromis, one lyretail anthias, green clown goby, orange diamond goby, mandarin dragonette and a yellow head goby.) I feed two cubes of either brine, mysis or bloodworms once a day and most if not all seems to get consumed before hitting the bottom of the tank. I have a few soft corals (fuzzy mushrooms, leather toadstool) but nothing else. My clean up crew includes 3 turbos, 5 nassarius, 6 blue leg hermits, 4 red leg hermits and a black scutus.

I've recently had a small battle with cyano on the substrate and have started using a phosban reactor to reduce my phospates. Other than this small amount of cyano, I have no nuissance algae to speak of. My main reason for wanting to reduce the nitrates is to have better water quality for the corals and attempt to host more sensitive specimens like SPS.

So what am I doing wrong? For a while I tried doing larger water changes but that didn't seem to help much. I always blow the rocks off with a power head and vacuum the substrate when I do the monthly water changes so that should be getting most detrius.

Most of my live rock came from my brother-in law who did not take care of his tank very well so I thought maybe those were saturated with high levels gunk but it's my understanding that nitrates are in the water column, not rock, so that shouldn't be the issue.

Help!

Thanks

[Randy Holmes-Farley]

My expectation is that the export methods are just not enough. More macroalgae and/or more light on it, maybe iron dose for the macroalgae, and more skimming would be my suggestions (since they will reduce phosphate too), but there are many methods such as those detailed in this article:

Nitrate in the Reef Aquarium
http://www.advancedaquarist.com/issues/august2003/chem.htm

and

Phosphorus: Algae’s Best Friend
http://www.advancedaquarist.com/issues/sept2002/chem.htm

[srfndoc]

So you don't think the live rock could somehow be contaminated causing the high nitrates (I didn't think so but wanted to be sure). I'm limited in space with my current sump so adding more chaeto may be tough although it's on a 24/7 lighting schedule so the amount of light it's getting is substantial. Since I'm exporting nitrates via skimming and macro, should I still do large water changes or is that a losing battle? Occasionally I re-do my aquascaping and do see alot of detrius underneath the live rock, could this be the souce of my high nitrates? What do most people do about getting that detrius (minus re-aquascaping every month).

I thought maybe building some type of structure for the rock to sit on so it's not on top of the sand but don't really like un-natural structures in the tank. I see huge tanks 500+ gallons with much more rock than I have sitting on sand yet they never seem to have an issue with high nitrates so maybe I'm barking up the wrong tree.

Thanks for the input.

[Randy Holmes-Farley]

No, contaminated live rock might cause elevated phosphate, but not 50 ppm nitrate. :)

Nitrate reduction by water change is usually a loosing battle. I show that here:

Water Changes in Reef Aquaria
http://reefkeeping.com/issues/2005-10/rhf/index.php

Occasionally I re-do my aquascaping and do see alot of detrius underneath the live rock, could this be the souce of my high nitrates?

It likely contributes, but without it the nitrate would likely still be elevated, but not as much.

[srfndoc]

Thanks for the link to the water change article. Very interesting. I think I'm going to bump up my monthly water change to 35% and continue to monitor just see it's affects.

Thanks

[Randy Holmes-Farley]

You're welcome.

Good luck. :)

[boxfishpooalot]

If you want to "see" where your nitrates are coming from do this:

Prepare a cup of new seawater mix. Then take some ditritus from under that rock, or anywhere. Use an eye dropper and add a drop to your newly made cup of salt water. Wait 3 days and check for nitrates, and phosphtes. You will be surprised.


I did the similar experiment but I added a pinch of sugar to fuel faster bacterial growth. Although the test for nitrate could have been messed up by the sugar I doubt it. Try that test :)