High Nitrate - Low Phosphate

[Comic_Reef]

Good afternoon,

First off, I am only leaving this here as a place for new and intermediate reefers to find some information. I by no means claim to be an expert but am only providing this "trial, error and success" steps that I took to solve a major problem that I do not see discussed very much, nor covered in many articles. Largely information I had to piece together and risk testing on my own. This is largely because it doesn't seem to be a very common problem. Seeing as I almost quit the hobby myself over it, I know that there is someone else out there struggling with the same problem and/or wanting to shut their system down.

The problem:
High Nitrates and Low Phosphates. By high nitrates I mean constantly rising, off the charts nitrates with phosphates at or "near-zero". Something like 100ppm NO3 and 0.02 phosphate.

The symptoms:
Nitrates will not come down. Phosphate will not go up. You have a good skimmer thats not pulling much, youve maybetried carbon dosing, a refugium or a denitrator, you're doing large water changes (50%+) multiple times a week but the nitrate just shoots back up within a day. You've cleaned everything you can, have no visible dead spots. Zero to very small amounts of Algae Growth. Water looks clean. Corals seem to be okay but don't thrive, some die fairly quick. SPS dies at an almost 100% rate.

The cause:
In short, it could be a lack of phosphate. For me it was GFO stripping all/most PO4. But for others it could be something else that disproportionately removes more PO4 that NO3.

Things to take into consideration:
Redfield Ratio. There is a lot of information here so I urge you to look into it if you are having this problem. The basics of it are as such: 106 Carbon to 16 Nitrogen (Nitrate) to 1 Phosphate. Now there is a lot of discussion surrounding Redfield Ratio and the importance of aiming for it, however it does illustrate that organisms in the home aquaria that dispose of Nitrate do require phosphate and carbon in order to do so. If you are at 100ppm NO3 and 0.02 PO4, you are at a NO3 to PO4 ratio of 5000:1. This will undoubtably hinder NO3 reduction.

The solution:
- Disable all phosphate removal media and go back to basics. Absolutely no GFO.

- Use the redfield ratio as a loose guideline and SLOWLY rebalancing the system through phosphate dosing. Depending on how out of whack your system is, you can do this from simply feeding more "high-phosphate" foods or dosing something like Brightwell's NeoPhos. I chose NeoPhos as I didn't want decomposing extra food to exacerbate the nitrate problem since I was over 100ppm Nitrate already.

- Test Phosphates daily. I recommend getting a Hanna ULR Phosphorous Checker to save you time. Pay attention to what youre bottoming out at. For me, my readings consistently came back 0.02. Most advice will tell you this is a great number to be at, however due to the steadfastness of this number, I believe that my results were actually zero. These tests can have a margin of error.

- Dose Safe Amounts of Phosphate Daily. if you are seeing a consistent zero or near zero measurement, dose a small amount of phosphate that, per instructions, should bring you up to say .04 total ppm. Test the following day and see where you are at. If you are back down to your zero/near zero levels, this is a "good sign". Something is consuming your phosphate. Something needed it. Do that for a week and if you keep coming back to zero daily, up the dose to bring you to .08 and test daily again. Your phosphate could be going one of a few places: Absorbed by rock, consumed by bacteria or consumed by algae. You may start seeing small, decreases in your nitrates at this point. If ever you test and the level hasn't come down to your original zero/near zero reading do not dose. You do not want to over do it because it can have negative side effects on your living organisms in high amounts.

- Pay attention to the algae/cyano. If ever a meaningful amount algae begins to pop up, stop dosing phosphate and see what happens to the algae. If it grows, there is still phosphate in the water, if it dies that means that there isnt. Essentially treat the algae like a visual representation of the denitrifying bacteria who are also vying for the same PO4 and NO3.

My end experience:
When I first dosed PO4, my tank was absorbing it at an absurd rate (.08 gone in 2 hours) and I had no algae. This gradually slowed down over time (.08 in 2 days) with small amounts of Cyano. My nitrate dropped from 100+ to a consistent 50 at about the 2 month mark with medium amounts of Cyano after each dose. At this point dosing once every 2-3 days. This tanked to 10ppm about a month later with a huge cyano outbreak after one of the doses. I siphoned this out as it signified the end of the need to dose as the PO4 was being mostly absorbed by algae. My phosphates still remain in the .04 range with Nitrate at 5.

Again, this I am not an expert nor claim to be. Just sharing my experience in hopes that it might help someone like me who was really struggling for a very long time with this issue. If it helps 1 person, I'm glad I took the time to post. Please call me out if something is wrong or you have any questions.

Happy reefing and happy new year

 

[sfin52]

Interesting

 

[Comic_Reef]

Interesting

Is that a good interesting or a bad interesting lol

 

[sfin52]

Never considered that before.

 

[Comic_Reef]

Never considered that before.

For me personally, it was my last attempt. I was in the "nothing to lose" stage since I had lost many of my coral slowly over time when this happened. GFO in my opinion can be just as damaging as a lot of other nutrient control methods. It's commonly warned not to overdose, and I personally found out why. It's something that, in my opinion has to be corrected quickly (putting some phosphates back in somehow) or, as in my case, it can cause a runaway nitrate problem.

 

[Super Fly]

So are you no longer needing to dose PO4?

I've been dealing w similar issue but my NO3 is 10 & PO4 was constantly at 0. Started dosing Seachem Phosphorous and PO4 finally started showing up after 2 weeks (0.03), on 3rd week it shot up to 0.18. So I ran GFO while stopping dosing which brought it down to 0.05 (then stopped GFO). Now PO4 is at 0.02... My Hanna checker always read 0 PO4 but since I began dosing few weeks ago it's gone up to 0.02 and has been holding there this week even though I stopped dosing. Now after reading ur thread, I'm debating whether to dose PO4 again but at reduced amount.

 

[Comic_Reef]

So are you no longer needing to dose PO4?

I've been dealing w similar issue but my NO3 is 10 & PO4 was constantly at 0. Started dosing Seachem Phosphorous and PO4 finally started showing up after 2 weeks (0.03), on 3rd week it shot up to 0.18. So I ran GFO while stopping dosing which brought it down to 0.05 (then stopped GFO). Now PO4 is at 0.02... My Hanna checker always read 0 PO4 but since I began dosing few weeks ago it's gone up to 0.02 and has been holding there this week even though I stopped dosing. Now after reading ur thread, I'm debating whether to dose PO4 again but at reduced amount.

With your nitrates at a less lethal level to most coral, I don't know if I would go to PO4 dosing to solve your nitrate problems. If your tester has shown true zero in the past then you're likely not seeing testing error unless you've vial is scratched or dirty. I would trust that 0.02 test in your case.

With less urgency, I would consider other methods of nitrate removal first and seeing what happens. If your nitrates continue to rise but PO4 doesn't, then I would consider it. Like anything in reefing go slow, upping it by 0.02 is enough to be able to get an idea of how your tank is handling the PO4 (leading to algae growth or absorbed by bacteria/rock).

In my case, my checker was reading 0.02 for every test for a few months. Before I began entertaining the idea of testing error.

 

[Super Fly]

With your nitrates at a less lethal level to most coral, I don't know if I would go to PO4 dosing to solve your nitrate problems. If your tester has shown true zero in the past then you're likely not seeing testing error unless you've vial is scratched or dirty. I would trust that 0.02 test in your case.

With less urgency, I would consider other methods of nitrate removal first and seeing what happens. If your nitrates continue to rise but PO4 doesn't, then I would consider it. Like anything in reefing go slow, upping it by 0.02 is enough to be able to get an idea of how your tank is handling the PO4 (leading to algae growth or absorbed by bacteria/rock).

In my case, my checker was reading 0.02 for every test for a few months. Before I began entertaining the idea of testing error.

I would agree on the PO4 test results. Now that my tank is consistently reading 0.02 PO4, would you think it's no longer necessary to dose PO4?

Been using Salifert NO3 test kit and readings are always borderline 5 or 10, hard to decipher but it never read above 10 so not really concerned about NO3 reduction but rather trying to maintain detectable levels of PO4... think I'll try a Hanna NO3 test kit for more precise reading.

 

[Comic_Reef]

I would agree on the PO4 test results. Now that my tank is consistently reading 0.02 PO4, would you think it's no longer necessary to dose PO4?

Been using Salifert NO3 test kit and readings are always borderline 5 or 10, hard to decipher but it never read above 10 so not really concerned about NO3 reduction but rather trying to maintain detectable levels of PO4... think I'll try a Hanna NO3 test kit for more precise reading.

Imo I would only dose PO4 again if my nitrates were high and I was desparate to get them down.

Here's why: You have to be okay with (almost hoping for) algae growth. Because at some point you are going to hit a dose where your denitrifying bacteria are going to not need more that a small amount for the lesser amount of nitrate in your tank. This is going to cause an algae explosion of some kind. For me, the week my tank jumped from 50ppm to 10ppm, I had a huge Cyano outbreak that caked everything and I had to siphon it a couple times. This was the point where I knew my tank was very close to rebalanced. The algae was consuming excess that the rest of the tank didn't need. You also don't want to over correct and then have to go back to GFO again which could replicate the problem again.

 

[Auto-pilot]

Also something to think about is a Phosphate level of 0 is really bad for coral. They need nutrients too!

 

[Comic_Reef]

Also something to think about is a Phosphate level of 0 is really bad for coral. They need nutrients too!

Precisely!!

 

[Dan_P]

In a recent small scale carbon dosing (calcium acetate) experiment (N=1), 7 ppm NO3 was reduced to undectable overnight after the phosphate concentration was increased to 0.2 ppm. There appeared to be little or no effect on acetate consumption. I have seen hints of this effect several times before but never like this. Maybe it is not so far fetched to link low phosphates in an aquarium to a “stuck” nitrate concentration. Never seemed to have this situation in my aquarium but will be on the look out.

 

[ReefSlice]

I'm having the exact same problem and did the exact same thing, but now I just have 20-30 ppm nitrates, .00-02 po4 still, lots of hair algae and cyano, and my corals are still pale and dying. Wish dosing po4 had worked out for me. Still trying, but no positive side effects in 6 months, just lots of algae and nitrates still won't stay down without carbon dosing.

 

[Comic_Reef]

I'm having the exact same problem and did the exact same thing, but now I just have 20-30 ppm nitrates, .00-02 po4 still, lots of hair algae and cyano, and my corals are still pale and dying. Wish dosing po4 had worked out for me. Still trying, but no positive side effects in 6 months, just lots of algae and nitrates still won't stay down without carbon dosing.

Some things I would consider: How often are you feeding, what is your alk at and how is your lighting. Barring some SPS species. 20ppm should be low enough that corals aren't paling out. I only saw this behavior above 50ppm. I'm guessing that something else is having an effect on them.

 

[O'l Salty]

I tend to agree that the Redfield ratio is a good target but I don't normally advocate dosing to get to those numbers. I've tried that and it ended with Dino's. Stability is the most important thing and I have found that dosing tends to create new problems because it throws your tank into an imbalanced state. There are other options to dosing like a bigger CUC , more or less water changes, feed less, feed more, algae reactor or macro algae in the sump. Don't try to "fix" everything you see happening in your tank immediately. Algae comes and goes. Some corals just die, it's the name of the game.

 

[Comic_Reef]

I tend to agree that the Redfield ratio is a good target but I don't normally advocate dosing to get to those numbers. I've tried that and it ended with Dino's. Stability is the most important thing and I have found that dosing tends to create new problems because it throws your tank into an imbalanced state. There are other options to dosing like a bigger CUC , more or less water changes, feed less, feed more, algae reactor or macro algae in the sump. Don't try to "fix" everything you see happening in your tank immediately. Algae comes and goes. Some corals just die, it's the name of the game.

I would absolutely agree with this if tinkering with adjustments. In my case, feeding more have minimal to zero effect, macro died immediately (no PO4), I burned through a large bucket of salt a month (on a 30 gallon tank!), CUC nearly all died (lack of algae). This was because the instability was already well into effect due to the gfo. With NO3 over 100 and PO4 at near zero, there was no way for the tank to stabilize normally without assistance in rebalancing. As I stated prior, I would absolutely try every thing else first, this should only be a backup option and should hopefully give those who may be facing the same thing something to consider before tearing things down.

 

[O'l Salty]

I would absolutely agree with this if tinkering with adjustments. In my case, feeding more have minimal to zero effect, macro died immediately (no PO4), I burned through a large bucket of salt a month (on a 30 gallon tank!), CUC nearly all died (lack of algae). This was because the instability was already well into effect due to the gfo. With NO3 over 100 and PO4 at near zero, there was no way for the tank to stabilize normally without assistance in rebalancing. As I stated prior, I would absolutely try every thing else first, this should only be a backup option and should hopefully give those who may be facing the same thing something to consider before tearing things down.

GFO is bad stuff. Surprised so many people use it. It stripped my water of phosphate and caused all kinds of trouble.

 

[Comic_Reef]

GFO is bad stuff. Surprised so many people use it. It stripped my water of phosphate and caused all kinds of trouble.

I vow never to touch the stuff again in a reactor barring a major PO4 spike for some reason. Even then it would likely get designated to a mesh bag in the sump

 

[Comic_Reef]

As an update, I am down to 2 ppm nitrate and added some fish to attempt to actually bring it up a bit to the 5-10ppm range.

As noted above, I stopped dosing when my nitrates showed less than 25 at which point I had a large cyano and turf algae outbreak. My guess is that with some PO4 finally lingering in the water column, it began to utilize it to break down nutrients locked in my sand bed. Both have since gone away about 80% naturally after about 3 weeks. Beefing up my clean up crew with a number of different snail species, an emerald crab and a blenny helped to achieve this.

I am not dosing any thing other than 2 part now. Using rock, filter floss/socks, MarinePure and Chaeto now.

 

[ADAM]

Great discussion/ info. Find myself in this predicament now. Zero PO4, Zero cyano, zero macro, zero GFO in system for months, few corals were looking “off” have been checking, checking, and checking some more. Got a new PO4 kit (Salifert) and consistently getting 0 PO4 as I was with prior kit, and somewhere btwn 50-100 on N03 color scale. I have increased feeding a little and let the cubes melt in a net sitting in the sump hoping that would help the PO4 but to no success after 2 weeks. I have ordered NeoPhos, which should be here today, to try dosing some PO4 as mentioned prior in the thread.

One product I see recommended a lot when people suspect metals, or have confined metals by ICP, is PolyFilter. PolyFilter will remove some metal however it removes all forms of phosphate at a much faster rate. Found this out the hard way after I applied the PolyFilter for elevated zinc and iron, the corals were not responding well and I was still blaming metals for the decline in health. After searching for more info I found that the PolyFilter is profoundly good at PO4 reduction versus metals absorption. Several high end colonies later I find that zero PO4 was likely the culprit the entire time.

Thanks for the Redfield Ratio info and the info from your personal experience with this matter.