Low phosphate high nitrate

[Duncan Tse]

Hey can someone come up with a game plan on what I can do at this point.

- 2 year old 40 gallon mixed reef running a reef octopus protein skimmer as the only filtration and 10% waterchange weekly
- 5 fish total
- was at 0.06 PO4 and 5ppm NO3
- mindlessly ran gfo in a reactor and PO4 would constantly be 0 so I upped my feeding by a lot feeding reef roids, pellets, and frozen daily
- was sitting at 0 PO4 and 25pm NO3 so I ended up stopping gfo
- currently at 0.06 PO4 and 25ppm NO3

What are some options in my situation to lower NO3?

 

[Fishnut]

How does your coral look? My tanks run with much higher NO3 and they are happy. Still looking for lower # try better export via larger water changes and feed less.

 

[Randy Holmes-Farley Verified Community Expert]

I wouldn't worry to much about the nitrate, but some organic carbon dosing is a fine plan.

 

[Dan_P]

Hey can someone come up with a game plan on what I can do at this point.

- 2 year old 40 gallon mixed reef running a reef octopus protein skimmer as the only filtration and 10% waterchange weekly
- 5 fish total
- was at 0.06 PO4 and 5ppm NO3
- mindlessly ran gfo in a reactor and PO4 would constantly be 0 so I upped my feeding by a lot feeding reef roids, pellets, and frozen daily
- was sitting at 0 PO4 and 25pm NO3 so I ended up stopping gfo
- currently at 0.06 PO4 and 25ppm NO3

What are some options in my situation to lower NO3?

If coral are OK, do nothing and observe nitrate decline. If nitrate remains elevated after 2-4 weeks, AND you judge it to be an issue, then try a remedy.

 

[Uncle99]

Phosphate is a bit hard to define accurately with hobby grade tests, a flux of 0.05 would not be uncommon.
So your 0 could actually 0.05, that’s fine in my mind, I run 0.15 phosphate with a 5ppm nitrate.

Like the carbon dosing idea. Go slow.

 

[Duncan Tse]

Hmm okay sounds like the 2 options for me would be to either carbon or just wait it out with weekly water changes and check if my nitrates are dropping.

Everything is doing fine so maybe I can just leave it alone if 25ppm nitrates is not an issue

A question with carbon dosing is that will it bottom out my phosphates? I heard if phosphates gets too low then that is a limiting factor and nitrates will not decrease.

 

[YankeeTankee]

Hmm okay sounds like the 2 options for me would be to either carbon or just wait it out with weekly water changes and check if my nitrates are dropping.

Everything is doing fine so maybe I can just leave it alone if 25ppm nitrates is not an issue

A question with carbon dosing is that will it bottom out my phosphates? I heard if phosphates gets too low then that is a limiting factor and nitrates will not decrease.

Like Randy said, I'd carbon dose here, start with a small amount then increase. Test as you go and just be prepared to dose some phosphate if that drops too low.

 

[Sgolden]

Feed with chunkier food for a while. Stuff that doesn’t silt the water .

 

[Duncan Tse]

Like Randy said, I'd carbon dose here, start with a small amount then increase. Test as you go and just be prepared to dose some phosphate if that drops too low.

Seems like there has to be some kind of balancing act if that happens. I do have a bottle of seachem phosphorous on hand if that does happen.

Another question is what would you try to maintain your PO4 levels to decrease NO3 from 25ppm to maybe 5ppm?

 

[Randy Holmes-Farley Verified Community Expert]

Seems like there has to be some kind of balancing act if that happens. I do have a bottle of seachem phosphorous on hand if that does happen.

Another question is what would you try to maintain your PO4 levels to decrease NO3 from 25ppm to maybe 5ppm?

The effect of organic carbon dosing on phosphate is much lower than phosphate due to denitrification driven by organics lowering nitrate and not phosphate, and the buffering of phosphate by phosphate bound to rock and sand . I’d just keep an eye on the phosphate. I would not dose any unless it drops below 0.03 ppm.

 

[mike550]

Not much to contribute to this thread, but carbon dosing seems more of a way to solve the effect (high nitrates) rather than managing the cause / source of high nitrates. Can water changes alone reduce the nitrate levels from 25 to 5 or would this require vacuuming sand, etc?

Not meaning to hijack the thread. Just trying to learn more. Thx

 

[Randy Holmes-Farley Verified Community Expert]

Not much to contribute to this thread, but carbon dosing seems more of a way to solve the effect (high nitrates) rather than managing the cause / source of high nitrates. Can water changes alone reduce the nitrate levels from 25 to 5 or would this require vacuuming sand, etc?

I would just add that I choose to organic carbon dose for more reasons than nitrate reduction. It spurs bacterial growth that acts as a food source for filter feeders, and may also be used directly by organisms including corals, sponges, etc.

 

[Duncan Tse]

The effect of organic carbon dosing on phosphate is much lower than phosphate due to denitrification driven by organics lowering nitrate and not phosphate, and the buffering of phosphate by phosphate bound to rock and sand . I’d just keep an eye on the phosphate. I would not dose any unless it drops below 0.03 ppm.

Okay I ask this because on my previous tank when I started carbon dosing, my tank was consuming about 0.13ppm PO4 a day and I had to dose phosphates.

- Tested PO4 2 hours after feeding and adding in 3.5mL seachem phosphorous
- PO4 was at 0.132ppm using the hanna ULR checker
- 24 hours later tested PO4 again and it's at 0.006ppm
- was dosing noxpox daily at 2mL

Does this sound normal to you? Was also running no gfo or any other source of filtration except the skimmer.

Noxpox dose didn't seem too high as redsea recommended to dose 3mL/25gallon if your nitrates are >10ppm

 

[Randy Holmes-Farley Verified Community Expert]

Okay I ask this because on my previous tank when I started carbon dosing, my tank was consuming about 0.13ppm PO4 a day and I had to dose phosphates.

- Tested PO4 2 hours after feeding and adding in 3.5mL seachem phosphorous
- PO4 was at 0.132ppm using the hanna ULR checker
- 24 hours later tested PO4 again and it's at 0.006ppm
- was dosing noxpox daily at 2mL

Does this sound normal to you? Was also running no gfo or any other source of filtration except the skimmer.

Noxpox dose didn't seem too high as redsea recommended to dose 3mL/25gallon if your nitrates are >10ppm

That does not mean the organisms were consuming phosphate, nor would I expect it to continue indefinitely.

Much and perhaps most of the phosphate added to a reef tank will bind to rock and sand, especially in a new tank rather than be used by organisms. One member showed that he needed to dose many ppm of phosphate to a container with only dead rock before he got a stable reading in the right range.

 

[Duncan Tse]

That does not mean the organisms were consuming phosphate, nor would I expect it to continue indefinitely.

Much and perhaps most of the phosphate added to a reef tank will bind to rock and sand, especially in a new tank rather than be used by organisms. One member showed that he needed to dose many ppm of phosphate to a container with only dead rock before he got a stable reading in the right range.

Okay I see that makes sense. So would you say that in that situation I should be dosing PO4 daily to maintain some trace amounts while dosing carbon and continue this regime until PO4 have stablized and NO3 have dropped down to a level that I am comfortable with?

Thanks for all the help!

 

[Randy Holmes-Farley Verified Community Expert]

Okay I see that makes sense. So would you say that in that situation I should be dosing PO4 daily to maintain some trace amounts while dosing carbon and continue this regime until PO4 have stablized and NO3 have dropped down to a level that I am comfortable with?

Thanks for all the help!

I would suggest maintaining at least about 0.03 ppm. If dosing is needed, I'd dose, or feed more.

 

[Uncle99]

I have been dosing Nopox for three years.
I used it to manage Nitrate after cycle from 50ppm to 5 ppm over 6-7 months.
I found that Nopox had little effect on phosphate. (Some effect Maybe, hard to tell in newer tanks.)
Reading 0 phosphate with any hobby grade test could mean 0.05 ish may be the actual reading.
What I did find out through an ICP test was that my hobby grade tests, API, Seachem and Hanna were all wrong, but that error would not be enough to cause any grief.

While I continue the use of Nopox, I have not used any type of phosphate removers in my DT for more than 2 years now and my phosphate, via ICP, stays on 0.15 consistently, whereas the Hana shows 0-0.04.

My corals have never looked better ever since I stopped chasing the tiny amount of phosphate in the water.

If my phosphate drops to zero,my Corals will tell me, just like they did when I tossed in a bag of Rowaphos a long time ago now.

 

[Duncan Tse]

I would suggest maintaining at least about 0.03 ppm. If dosing is needed, I'd dose, or feed more.

Sounds like a plan. Thanks!

I have been dosing Nopox for three years.
I used it to manage Nitrate after cycle from 50ppm to 5 ppm over 6-7 months.
I found that Nopox had little effect on phosphate. (Some effect Maybe, hard to tell in newer tanks.)
Reading 0 phosphate with any hobby grade test could mean 0.05 ish may be the actual reading.
What I did find out through an ICP test was that my hobby grade tests, API, Seachem and Hanna were all wrong, but that error would not be enough to cause any grief.

While I continue the use of Nopox, I have not used any type of phosphate removers in my DT for more than 2 years now and my phosphate, via ICP, stays on 0.15 consistently, whereas the Hana shows 0-0.04.

My corals have never looked better ever since I stopped chasing the tiny amount of phosphate in the water.

If my phosphate drops to zero,my Corals will tell me, just like they did when I tossed in a bag of Rowaphos a long time ago now.

Wow nice tank! I'm surprised the icp test was so off from the hanna ulr checkers

 

[Eggpaul]

I'm having a similar problem. I notice some corals are not too happy and losing color. My phosphates were .09 so I turned on the GFO, now they are 0.00 and Nitrates were 25. Last night I did a large water change and also turned off the GFO to build up phophates.

I don't want to keep turning the GFO off/on. Should I use less GFO and keep it on?

Also , I check Phosphates with the Hanna test kit. Even when it says 0.00 , I still get a lot of algae build up on my front glass every few days.

 

[Uncle99]

IMO, Your phosphate was fine at 0.09 (0.03-.15).
I run nitrate at 6ppm using Nopox.
I run Phosphate at .15. - .20 for three years this build
Pull the GFO, watch your tests, do nothing until to reach say .20, then bring the GFO back on line to reduce a bit slowly.
See what the tank can do on its own.