NO3/PO4 Ratio

[Anthrax15]

Right now I am dosing 10ml a day of NO3 and 2.2ml of PO4 in order to keep things stable. Tank is going on 5 months old but my PO4 numbers are constant then randomly drop. For 2 days or so I can maintain 0.09-0.10 and then it will drop to 0.02. I am trying to keep NO3 around 5-10 and PO4 around 0.07-0.10. I am using NYOS for Nitrates and Hanna ULN for Phosphates.

Do I need to dose these in a specific ratio or keep the parameters differently? I am using a doser for PO4 and manually dosing NO3. Tank is also having a Cyanobacteria issue at the moment.

 

[SMSREEF]

Right now I am dosing 10ml a day of NO3 and 2.2ml of PO4 in order to keep things stable. Tank is going on 5 months old but my PO4 numbers are constant then randomly drop. For 2 days or so I can maintain 0.09-0.10 and then it will drop to 0.02. I am trying to keep NO3 around 5-10 and PO4 around 0.07-0.10. I am using NYOS for Nitrates and Hanna ULN for Phosphates.

Do I need to dose these in a specific ratio or keep the parameters differently? I am using a doser for PO4 and manually dosing NO3. Tank is also having a Cyanobacteria issue at the moment.

I dose them independently. I find I need to dose a lot more phosphate than nitrate.

My goal since I have a new tank and fought Dino’s and chrysophyte is NO3 of 5-10 and PO4 of 0.05 to 0.1

I actually add phosphate to my top off water so the tank is getting a little bit multiple times a day. I figured out what my tank uses in a week and added it. Now I test only once a couple times a week and do a correction if I fall below 0.05ish - lower if green algae is growing on glass. I use the algae as an additional guide added to the actual phosphate result on Hanna test.

Nitrate, I test and dose once a week if needed. I also took my protein skimmer out.

I found manual removal/suctioning the cyano out helps a lot.
Also CUC will help.

 

[face]

Phosphate will swing a lot more because it is 100x lower concentration So it is harder to keep a low concentration stable than a much higher one. If anything utilizes or absorbs PO4 it will swing easier.

 

[Randy Holmes-Farley]

There is no reason, theoretical or empirical, to dose them in any given ratio since tanks can use them in independent processes, such as denitrification (consumes nitrate) or binding to rock and sand (phosphate).

 

[Randy Holmes-Farley]

Phosphate will swing a lot more because it is 100x lower concentration So it is harder to keep a low concentration stable than a much higher one. If anything utilizes or absorbs PO4 it will swing easier.

I'm not sure I agree with that reasoning, but I've not see enough data to know if the premise of more stable nitrate is true or not.

The phosphate concentration is heavily buffered in most tanks by binding to rock and sand, while nitrate is not.

Organisms generally consume a lot more N than P, so just because there is more present doesn't mean it would be more stable.

 

[Anthrax15]

There is no reason, theoretical or empirical, to dose them in any given ratio since tanks can use them in independent processes, such as denitrification (consumes nitrate) or binding to rock and sand (phosphate).

Would there be any reason that the PO4 would be stable for 2 days then suddenly drop? I've seen this pattern twice.

 

[face]

Would there be any reason that the PO4 would be stable for 2 days then suddenly drop? I've seen this pattern twice.

My guess is if any algae goes into bloom it’s going to drop the PO4 a lot faster. But I could be wrong as was stated above.

 

[face]

I'm not sure I agree with that reasoning, but I've not see enough data to know if the premise of more stable nitrate is true or not.

The phosphate concentration is heavily buffered in most tanks by binding to rock and sand, while nitrate is not.

Organisms generally consume a lot more N than P, so just because there is more present doesn't mean it would be more stable.

Is it always heavily buffered? I notice lots of reef tanks flip between undetectable and about .03ppm very easily. In general it seems much harder to keep a stable PO4 than nitrate In my experience at least. Maybe it is buffered if you have been running a higher concentration for an extended period?

 

[Randy Holmes-Farley]

Would there be any reason that the PO4 would be stable for 2 days then suddenly drop? I've seen this pattern twice.

Test error, or a variable feeding and testing timing.

 

[Randy Holmes-Farley]

Is it always heavily buffered? I notice lots of reef tanks flip between undetectable and about .03ppm very easily. In general it seems much harder to keep a stable PO4 than nitrate In my experience at least. Maybe it is buffered if you have been running a higher concentration for an extended period?

That’s at the limit of testing. Even if it isn’t test error, if you test at the right time after feeding, you may get a higher value than a few hours later.
The buffering takes a little time, and in a tank with silica sand and old live rock, will be smaller.

 

[X-37B]

For me if you have algae that grows on the glass you have enough po4.
I dont even test much anymore as its always .02-.06 and sometimes reads 0 on the hanna.
If you feed pellets and test an hour later your po4 will generally be higher, mine always is.
For the first 13 months my tank was running po4 was 0-.02 and no3 2ish.
I dosed both po4 and no3 for awhile but stopped as I did not see any noticable difference in my tank.
I decided to feed more and let the numbers be what they are as long as my tank looked good.
I test no3 and po4 once a month as a reference and log it.
Tank is 16 months now.
At 14 months through today po4 runs.04-.08 and no3 10ish.
I have been carbon dosing a small amount of a sugar,vinegar, iron mix, and p04 has been .03-.04 and no3 <10.
This is more for the corals and bacteria than to control po4 and no3.
For my tank this is a good range.
A balance of fish, feeding, and proper export is a better approach than dosing po4 and no3, imo.