Freaking nitrates wont drop

[civileng68]

I'm so frustrated. I am experienced at this at this point and completely feel like I'm failing.
My tank is well established (over 1 1/2 years old).
My water is changed frequently.
Here are my stats:
55 gallon column
150W MH
2X65 actinic
18 gallong refugium with Micro Algae and broken live rock.
Stock:
2 False Percs
1 Purple Dottyback
1 Blenny
1 Cleaner Shrimp
30 Snails
10 Hermits
3 Sand Cleaning Cucumbers
50 lbs of Live Rock.
Frogspawn
Green Bubble Coral
Xenia (which is nearly growing out of control)
Zoas
Mushroom

[hr]
Test results:
Ammonia - 0
PH - 8.2
Alk - 3.5
Calcium 240
Nitrites - 0 (never had a single Nitrite in any testing since having tank)
Phosphates - 0 (also never had a single Phate since having tank)
Nitrates - 20 (and that's after water changing).
My Nitrates never go below 20 and ALWAYS go up from there.
I tested my water (I use RO water from home) before putting it in the tank and all of the numbers are perfect, and 0 NITRATES.
I have not however tested it after putting the salt in it before putting it in the tank. However i doubt it's a bad batch of salt because this is a constant problem, even through MANY MANY different bags of salt.
The only thing is if the salt company itself has a NItrate situation in their salt on a regular basis, which I doubt it does.
I use REEF CRYSTALS salt.
I haven't had anything die to my knowledge in the tank.
Other than the Nitrates, the tank seems to be doing well. I get a BEAUTIFUL coating of Corralline on any rock that goes into the tank. I mean, my tank is loaded with it.
I just added some LR last week and it's already starting to coat.
I dont use ANY SUPPLEMENTS IN MY TANK OTHER THAN CALCIUM WHEN NEEDED BUT HAVEN'T USED IT IN A LONG TIME.
What can be keeping my Nitrates from dropping?

 

[bang guy]

Could be any combination of the following:
Overfeeding
Inadequate waterflow
Inadequate diversity in the live rock

 

[civileng68]

Originally Posted by Bang Guy
Could be any combination of the following:
Overfeeding
Inadequate waterflow
Inadequate diversity in the live rock

Well I think I've got a pretty good diversity in LR, I guess?
I think my water flow is pretty good (I have the water flowing in from the HOB fuge, I have the two nozzles shooting in two directions from the sump, and I have a nice powerhead on the other side of the tank shooting to the other side which moves back and forth getting nearly every part of the tank.
Now, OVERFEEDING COULD be part of the problem but I've REALLY cut back. Wouldn't the ammonia spike a little though if this were the case?

 

[bigarn]

personally, if the nitrates stay below 40 i wouldn't worry to much.

 

[civileng68]

Originally Posted by bigarn
personally, if the nitrates stay below 40 i wouldn't worry to much.

yeah I agree, but, they wont. They'll keep going up again. I know enough about this thing (even though I'm still young at it) to know that just like thunder with lighting, there's a definate reason for the increase. It's like a puzzle piece that I can't find.
I thought by adding the fuge, the micro algae would help reduce the trates but it hasnt.

 

[bang guy]

Originally Posted by civileng68
yeah I agree, but, they wont. They'll keep going up again. I know enough about this thing (even though I'm still young at it) to know that just like thunder with lighting, there's a definate reason for the increase. It's like a puzzle piece that I can't find.
I thought by adding the fuge, the micro algae would help reduce the trates but it hasnt.
It will, but that's a long term solution.
I forgot to mention the Skimmer. A good skimmer will remove DOCs before they break down into phosphate & Nitrate.
Do you think you have more than 1000gph of waterflow in your tank?
How did you cure the live rock or was it pre-cured?

 

[civileng68]

Originally Posted by Bang Guy
It will, but that's a long term solution.
I forgot to mention the Skimmer. A good skimmer will remove DOCs before they break down into phosphate & Nitrate.
Do you think you have more than 1000gph of waterflow in your tank?
How did you cure the live rock or was it pre-cured?

Oh I forgot to mention I have an Aqua C Remora Skimmer.
I'll check to see if I have a 1,000 gph waterflow. If not, should I try to get it to that level? Also, is there a method to the waterflow? Do i want to create one current (such as keeping the water moving a certain direction, or just let it go in any area that isn't getting movement?
My Life rock is pre-cured. Now, the thing is, before adding some LR this past week (last week), I hadn't added any in a long time (nearly a year) and I was still getting high nitrates.
The rock I get is from my LFS, and is well cured. In fact, when they get it, I wait until they have time to cure it very well. I even go to the back to pick it out and smell it before I buy it.
So you think it could be waterflow? How does that keep the nitrates higher? I just like to know this stuff so I know how things work?
I just figured if it was something decaying or something due to overfeeding it would show a spike in ammonia.
Now, the one thing I did think about was this................my cucumbers are pretty new and before them, I haven't had anything stir the sand around well. My hermits dont move the sand much and even my cucumbers dont really stir it up. I've notice in some areas of my tank, near one corner in particular, my sand is darker. It's NOT algae or anything like that, it's just darker (almost dirty looking). Could this be due to water flow or the fact that when I siphon out old water I dont get into the sand to clean it. I just always figured that was "good" bacteria and I shouldn't disturb it. What do you think about that as being a possible cause?

 

[bonebrake]

Are these nitrates corroborated with a different test kit?
You could simply be getting bent out of shape by a faulty or outdated test kit.
Take your water to a LFS and have them test it and buy a new test kit if they give you a different result.
:joy:

 

[cymbal67]

you can try adding mangroves to your fuge, they absorb trates. and also a phos reactor with nitrate removing media in it instead of phos ban.