Low nutrients but high nitrates??

[blackthunda77]

Problem im encountering is that i cant get my nitrates below 20ish. I dont feed heavily, flakes once a day on a auto feeder and a cube of mysis in the evening when im home. I do weekly water changes, or bi weekly of about 30 gals at a time. I run a reactor with GFO and one with carbon. Also running a Reef Octopus 5000INT which is rated for over 500 gal. Its almost as if i have a nutrient poor system but am still testing high on nitrates. I have some sps frags like an xfactor monti and an idaho grape as well as a red unnamed acro which are very pale. My hammer frag is a big transparent as well. Im kind of confused as if it has to do with my nutrients or lighting (2 - 250 watt radiums on lumen max elite reflectors) or something else.

Ive started dosing nopox as a carbon source and started feeding red sea reef energy a+b. I mean, now that i think of it, i dont even remember the last time i had to scrape my glass for algae (green or corraline). Coraline is also really slow to grow. Have almost none on my rocks and very minimal amounts on my black background or on my powerheads. The lack of algae and coraline would be cool, if only my corals were doing better. Anyone have any input? At the moment i have even cut down on my carbon and gfo reactors in case they are stripping the water too clean. But again, why the high nitrates?

Not really sure what else to try at the moment. The tank is a 200 Gal display with an 80 gal sump. Minimalist aquascape with 2 perculas, a threadfin cardinal, 2 disbar and 1 lyretail anthias, half a dozen to a dozen smallish sps frags, couple trumpet corals, a hammer coral, some scolys, and a large Ritteri anemone.

Ammonia and Nitrites - undetectable
Phosphates - undetectable
salinity - 35ppt
alk - 9
calc - 420
mag - 1380

Nitrates - 20ish or less.

 

[4ddiction]

Have you tried feeding more?

 

[blackthunda77]

I have, but at the same time im trying to get my nitrates to come down. Seems like they are stuck where they are. Seems like im fighting two exactly contradicting battles at the same time. To feed or not to feed...

 

[gbru316]

What nitrate test kit are you using?

Pale corals are indicative of either nutrient deficiency or extreme lighting. Your lighting doesn't seem extreme

FWIW, I've had the best luck with Red Sea's nitrate kit. The results are, by far, the easiest to read (and I've tried just about everything).

 

[blackthunda77]

I test with an api kit to see if I get any readings, if I do then I double check it with my salifert test.

I regards to lighting, the bulbs are about 8" above the water and the tank is a out 24" tall. It's possible that the guy I got most of these frags from, the montis and hammer, was running either a higher nutrient tank or the corals we shaded? But he's a good friend and I know his tank which is a similar dimension to mine and he too is running radiums...which is why I'm leaning towards a nutrient issue, which then leads to my initial question. Can I have a nutrient deficiency while still testing with elevated nitrates? Are they two different things?

 

[gbru316]

The API NO3 kit is notorious for erroneous measurements. I had a similar problem years ago (same test kits) and when I switched to Red Sea, found out my NO3 was under 5 ppm. The gradations between most NO3 kits can be really difficult to distinguish.

But now that I think about it (I've been out of the hobby for about a year, trying to get back in at some point), I think it is possible.

It's been reported that having absolutely no phosphate can cause pale corals. In those cases, though, NO3 was also undetectable. Not sure if the presence of NO3 would change it.

 

[AcroNewbie]

From what I understand (and this is just what I have read, not a scientific statement), NO3 reduction depends somewhat on PO4, in that bacteria requires both to reproduce, which is what dosing NOPOX is trying to do which is to add a carbon source to help bacteria reproduce because NOPOX dosing is assuming that your tank is carbon limited, so if you have no phosphates, dosing NOPOX is not gonna do much because your bacterial population is likely phosphate limited and all NOPOX is gonna do is saturate your water with a carbon source which may or may not be a good thing.
Another reason that might be contributing to your problem is the minimalist scape, which I presume leaves very little anaerobic areas in your tank for denitrifying bacteria to colonize. These denitrifying bacteria is a major contributor to reducing Nitrate in a tank, do you have any anaerobic (low flow) areas in your tank with live rock/porous media? Most successful reefers on here using the minimalist scape usually have a ton of high-efficiency media in their sump such as Siporax or Matrix, which is a highly porous artificla material that offers a lot of surface areas (both aerobic and anaerobic) for bacteria to colonize, which allows them to skip loading up on live rock.

 

[blackthunda77]

So are you saying that my denitrifying bacteria is not gaining a strong hold because it's limited by my low phosphates? Even though I have plenty of nitrates? Am i understanding your comment correctly?

Also, your right about the porous media, my next step is to add some siporax or matrix. However, it's not like I have NO rock. I'll try to post a pic.

 

[blackthunda77]

 

[gbru316]

So are you saying that my denitrifying bacteria is not gaining a strong hold because it's limited by my low phosphates? Even though I have plenty of nitrates? Am i understanding your comment correctly?

Yes.

 

[blackthunda77]

Yes.

Sooo...what? Feed more even though I have elevated nitrates? I turned down my GFO and activated carbon to barely a trickle. I might just shut it off completely for a while. I'm also still dosing DIY nopox and red sea reef energy.

 

[AcroNewbie]

Sooo...what? Feed more even though I have elevated nitrates? I turned down my GFO and activated carbon to barely a trickle. I might just shut it off completely for a while. I'm also still dosing DIY nopox and red sea reef energy.

The low phosphate is limiting the effectiveness of your NOPOX dosing, I think you should reduce the amount of GFO used rather than reduce the flow, if you reduce the flow through the GFO it will just clump and harden, keep the flow but reduce the amount of GFO in the reactor or take it off completely. Additional feeding may help but it will also add more nitrates, judging from your pic it looks like the rocks are in pretty open areas (i.e. well aerated), which means there probable isn't much denitrification going on, adding the siporax and matrix will definitely help just remember to not put them in high flow areas and be patient, it takes time for the media to get colonized and start producing noticeable effects, you can seed the media with bottled bacteria but it will still take some time.
Also Vacuuming your sandbed may help, it looks to be pretty large grains, which means it will trap a lot of gunk in there.