Dosing No3 and Po4????

[mattgsa]

Very interesting discussion. This is something I have been researching for awhile. now. I remember not that long ago, reading the Tank of the Month over on Reef Central. There were some amazing SPS dominated tanks, and every single one of them would say their NO3 and PO4 are at zero. Now it doesn't seem to be possible to grow coral with out higher levels of Nitrates. Unless using Zeovit which was not around at the time. So what changed?

 

[Randy Holmes-Farley Verified Community Expert]

Very interesting discussion. This is something I have been researching for awhile. now. I remember not that long ago, reading the Tank of the Month over on Reef Central. There were some amazing SPS dominated tanks, and every single one of them would say their NO3 and PO4 are at zero. Now it doesn't seem to be possible to grow coral with out higher levels of Nitrates. Unless using Zeovit which was not around at the time. So what changed?

Mostly it's the concept of what 0 means, IMO. When I started, no phosphate kit could read accurately below 0.03 ppm, and we did not have nearly the capacity to easily get that low that modern tools give.

 

[jduong916]

I have a question about this redfield ratio thing. It says 16 to 1 N to P, So if phosphate is at .05 should nitrate be at .8 ppm. I normally see people shoot for 5 ppm nitrate and .05 ppm phosphate, that doesn't seem to match the ratio. Am I misinterpreting something.

 

[Sallstrom]

I have a question about this redfield ratio thing. It says 16 to 1 N to P, So if phosphate is at .05 should nitrate be at .8 ppm. I normally see people shoot for 5 ppm nitrate and .05 ppm phosphate, that doesn't seem to match the ratio. Am I misinterpreting something.

That ratio is N,P and C in phytoplankton. Not in seawater.

/ David

 

[Randy Holmes-Farley Verified Community Expert]

I have a question about this redfield ratio thing. It says 16 to 1 N to P, So if phosphate is at .05 should nitrate be at .8 ppm. I normally see people shoot for 5 ppm nitrate and .05 ppm phosphate, that doesn't seem to match the ratio. Am I misinterpreting something.

I do not think the redfield ratio should be used to target desirable levels. Target nitrate and phosphate independently to optimal levels, IMO.

 

[jduong916]

So let's say my phosphate is at .05 and my nitrate is at .5 ppm. Can I just raise the nitrate to 5 ppm and leave the phosphate where its at?

 

[Randy Holmes-Farley Verified Community Expert]

So let's say my phosphate is at .05 and my nitrate is at .5 ppm. Can I just raise the nitrate to 5 ppm and leave the phosphate where its at?

That’s what I would do. [emoji3]

 

[Sallstrom]

Very interesting discussion. This is something I have been researching for awhile. now. I remember not that long ago, reading the Tank of the Month over on Reef Central. There were some amazing SPS dominated tanks, and every single one of them would say their NO3 and PO4 are at zero. Now it doesn't seem to be possible to grow coral with out higher levels of Nitrates. Unless using Zeovit which was not around at the time. So what changed?

From what I have seen too low nitrate often leads to cyano bacteria and corals near the edge of giving up.
So dosing nitrate and phosphate has help us a lot at work. We use KNO3 and KH2PO4 from a fresh water/plant shop.

For potassium, we see a small decline in our Triton ICP test in most of our tanks. Haven't seen any increase of K after long term dosing of for example KNO3, but maybe our doses are too low to make any difference.


/ David

 

[hatfielj]

So let's say my phosphate is at .05 and my nitrate is at .5 ppm. Can I just raise the nitrate to 5 ppm and leave the phosphate where its at?

You might find that your phosphate drops after you start supplementing the nitrates. I had this happen to me. I've since started started dosing phosphates too.

 

[Sallstrom]

So let's say my phosphate is at .05 and my nitrate is at .5 ppm. Can I just raise the nitrate to 5 ppm and leave the phosphate where its at?

I agree with Randy. But keep an eye on the phosphate. Sometimes adding nitrate leads to very/too low phosphate in the long run.

/ David