Redfield Ratio Dosing

[Aaron Stone]

The long story not so short: For about 8 months my coral have been pail, especially SPS, and growth has been slowing significantly. Most of the LPS had either stopped growing or in the case of the acans had begun to melt away. Reading up I determined that the tank was TOO clean, nitrates and phosphates undetectable. I tried feeding significantly more, but it didn't seem to really help. The bio-load on the tank is pretty small with only 4 medium sized fish. Reading up some more I decided to try nitrate dosing with potassium nitrate. For the first day or two this seemed to help, then some of the SPS started to really react badly. I figured this was due to the remainder of the phosphates being used up as nitrates became available. The reaction that I saw from the SPS was the same that I had seen a couple years back when I had used too much Phosban and stripped the phosphates too fast. I stopped dosing nitrates, the system stabilized, and a couple of weeks ago I just turned off the skimmer. This seems to be helping with coloration, growth, and overall apparent coral health. For now. This goes against everything that I have ever done in the hobby and am wondering at the long term wisdom to my solution, but old dogs do learn new tricks. I know there are some beautiful tanks out there that run without a skimmer, but...

So now my question: has anybody formulated a mixture to dose that will provide approximately the Redfield Ratio of nitrates and phosphates?

Tank and Filtration:
75 Gallon + 20 Gallon Sump Mixed Reef
75 lbs Live Rock
XPort Bio Plate - similar to marine pure
Octopus 100Int Skimmer
Big old ball O'Chaeto

 

[slicko]

The problem with the "redfield ratio" is its a ratio of CNP of oceanic plankton, this does not apply to the reef aqauria. every carbon based living organism has a CNP ratio even you and me but you would need to know the type of bacteria (s) strain in your reef aqaurum and then find out the CNP ratio to dose accordingly.

how many and what type of fish are in your system?

 

[Aaron Stone]

I apparently need to read up more on it. I was under the assumption that the 16:1 ratio (ignoring carbon for a moment) was a more general ratio applicable to marine life. My thoughts are less toward bacteria and more toward the photosynthesis of zooxanthellae.

 

[Aaron Stone]

Four fish:
3" Maroon Clown
3" Yellow Tang
4" Lawnmower Blenny
4" Sixline

 

[Randy Holmes-Farley]

I would not assume that dosing the redfield ratio is needed or desirable. There are exports taking place in reefs that do not follow this ratio at all.

Denitrification, for example, uses huge amounts of nitrate and very little phosphate, while phosphate incorporation into calcium carbonate skeletons, surfaces, precipitates uses no nitrate.

 

[Aaron Stone]

Thank you both very much, this is why I ask questions. Does anybody see any long term issues with leaving the skimmer off so long as nutrients stay in check?

 

[Randy Holmes-Farley]

Thank you both very much, this is why I ask questions. Does anybody see any long term issues with leaving the skimmer off so long as nutrients stay in check?

Skimmers do much more than export nutrients. Aeration and removal of organic matter than can be yellowing or toxic, for example.

 

[slicko]

imo i would add more fish. not only do you get the added enjoyment of extra life you also get some more nutrients to feed the coral, i beleive fish poo is some of the best stuff coral can have.

 

[Bayinaung]

The long story not so short: For about 8 months my coral have been pail, especially SPS, and growth has been slowing significantly. Most of the LPS had either stopped growing or in the case of the acans had begun to melt away. Reading up I determined that the tank was TOO clean, nitrates and phosphates undetectable. I tried feeding significantly more, but it didn't seem to really help. The bio-load on the tank is pretty small with only 4 medium sized fish. Reading up some more I decided to try nitrate dosing with potassium nitrate. For the first day or two this seemed to help, then some of the SPS started to really react badly. I figured this was due to the remainder of the phosphates being used up as nitrates became available. The reaction that I saw from the SPS was the same that I had seen a couple years back when I had used too much Phosban and stripped the phosphates too fast. I stopped dosing nitrates, the system stabilized, and a couple of weeks ago I just turned off the skimmer. This seems to be helping with coloration, growth, and overall apparent coral health. For now. This goes against everything that I have ever done in the hobby and am wondering at the long term wisdom to my solution, but old dogs do learn new tricks. I know there are some beautiful tanks out there that run without a skimmer, but...

So now my question: has anybody formulated a mixture to dose that will provide approximately the Redfield Ratio of nitrates and phosphates?

Hi Aaron,

I experienced something similar as well and had to stop nitrate dosing immediately. Thus far what I have done is reduce phosphate reduction, doubled my feeding, and stopped carbon dosing. I have also cut back skimming, running it at the same time as photo period. As a result phosphates have nudged back up a bit now. I will see how the corals react to this current change and experiment with dosing in a few weeks.

I have been looking for people who are dosing N and P on forums. I found some people are dosing a product that has a mixture of nitrates and phosphates. I found one person dosing both N and P in a ratio of 10 to 1. His acros have outstanding colour so he's doing something right. Those are my current thoughts on this. Hope that helps.

 

[Rick.45cal]

I'll dose KNO3 and Phosphate (brightwell NeoPhos) when my tank needs it. I will dose enough KNO3 to bring the tank to 2.5ppm NO3 and enough NeoPhos to bring the phosphates to .02ppm. It's worked very well for me. (I just dosed both today)

 

[Bayinaung]

sweet! let us know how it went!

 

[O'l Salty]

I apparently need to read up more on it. I was under the assumption that the 16:1 ratio (ignoring carbon for a moment) was a more general ratio applicable to marine life. My thoughts are less toward bacteria and more toward the photosynthesis of zooxanthellae.

https://buddendo.home.xs4all.nl/aquarium/redfield_eng.htm

I'm going to experiment on one of my tanks with this theory. The dosing calculator will be helpful.

 

[Osteoclast]

I agree that adding more fish will likely improve your issues. I have been in your shoes previously with running a "too clean" tank. Do not stop skimming, continue your filtration, and water change schedules. Adding fish and increasing feeding will eventually cause a favorable increase in coral growth. Go slowly and I believe you will have favorable results. Using the Redfield ratio as some critical formula for successful reef keeping is simplistic in my view. Biology is much more complicated than a simple ratio. Best of luck.

 

[O'l Salty]

I agree that adding more fish will likely improve your issues. I have been in your shoes previously with running a "too clean" tank. Do not stop skimming, continue your filtration, and water change schedules. Adding fish and increasing feeding will eventually cause a favorable increase in coral growth. Go slowly and I believe you will have favorable results. Using the Redfield ratio as some critical formula for successful reef keeping is simplistic in my view. Biology is much more complicated than a simple ratio. Best of luck.

My motivation for experimenting with the Redfield ratio is only for algae control. Allegedly keeping this balance will reduce or eliminate nuisance algae

 

[Rick.45cal]

https://buddendo.home.xs4all.nl/aquarium/redfield_eng.htm

I'm going to experiment on one of my tanks with this theory. The dosing calculator will be helpful.

Interesting link

 

[Randy Holmes-Farley]

My motivation for experimenting with the Redfield ratio is only for algae control. Allegedly keeping this balance will reduce or eliminate nuisance algae

I'm not inclined to believe that, but it's a fine experiment. In any case, the ratio in the tank is not going to be the same as the dosed ratio since consumption in a reef tank does not follow a redfield ratio due to denitrification.

 

[Bayinaung]

I resumed dosing, this time both N and P using Seachem Flourish Phos and Nitrates (2 separate products). I began by dosing greater than the Redfield ratio, about 25N to 1P since I had some low end phos as per test kit (~0.05). That's 2.5ppm N and 0.1P.

Well, 2 days later my N is still O and P is now O. So I moved to Redfield ratio - 16-1. Still 0. So I went to the ratio this aussie guy was using - 10-1. two days later, Eureka! I have N! it's showing to be 5ppm today (was dosing 2.5ppm). Phosphates are either 0 or 0.05ppm.

I have noticed that my algae now has color - it is now green whereas it was grey previously and blended in with the rock. I'll measure tomorrow before dosing.

 

[mcarroll]

IME you will get results just by having a consistent source of nitrogen going into the system – there are no magic numbers. (All the organisms you're thinking about are excellent at conserving/recycling nitrogen....so nitrates in the water isn't a requirement.)

The only bad thing about PO4 as far as I can tell is that running too low will cause a range of bad things.....among them coral metabolism issues and algae becoming generally unpalatable as well as possibly turning toxic and killing off CUC.

So IMO, consistent, non-zero levels of both is the important factor.

And FWIW, I also quit nitrate dosing when I had a polyp in my Favia colony "emplode". I don't really have a way to confirm it, but from what I've read, that reaction is consistent with the coral losing control of the zooxanthelae. Non-pigmented tissue on the coral turned nearly black from the density of zoox after I had been dosing for a little while, so I knew I was pushing it at least to some extent.

 

[Bayinaung]

And FWIW, I also quit nitrate dosing when I had a polyp in my Favia colony "emplode". I don't really have a way to confirm it, but from what I've read, that reaction is consistent with the coral losing control of the zooxanthelae. Non-pigmented tissue on the coral turned nearly black from the density of zoox after I had been dosing for a little while, so I knew I was pushing it at least to some extent.

Interesting. what were your nutrient levels when this happened? Did your SPS turn brown from too much zoox?

 

[mcarroll]

They've always been low because I've rarely had many fish in the system...sometimes no fish at all. But after so many years, including the last 3-4 with some neglect, a bit of PO4 had accumulated...nothing tremendous (maybe 0.8? I kinda forget.) but still enough to make the situation ripe. In a nutshell, NO3 was persistently low and I ended up with an outbreak of #chrysophytes.

I can't remember the exact date where the polyp blew out (I need to go back through photos) but looking back at my testing diary, the peak readings I had were:
0.63 ppm PO4 along with 2 ppm NO3

Then three weeks later of 10 mL of KNO3 + 5 drips of amino acid per day...
0.05 ppm PO4 along with 25 ppm NO3

I did find the post where that happened in my system thread: post #59

I'm not sure if I posted a pic of this Favia though...I have one from September on there where he was still fine. And that post I just linked is from October. So it'll be interesting if I can dig up the date on the photos with the "emploded polyp".

That's what I was saying about the zoox....they went past brown to nearly-black though!

I failed to mention that this polyp was also the least-lit on the colony (facing away from the lights), and the flow back there probably isn't what it was either.