Balancing the chemical compounds in your reef: Do you pay attention to the nitrate-phosphate balance?

[Randy Holmes-Farley]

I’m not really sure about this, but I find it interesting that almost everyone that gives their ranges and says they don’t care about ratios have a ratio of about 1 to 100 with the ranges that they keep.

Largely that likely stems from foods bringing in a ratio where there is much more N than P, since that is what organisms are made of.

 

[vlangel]

I test nitrates and Phosphates and compare their numbers because I have a lot of macroalgae. I am aware of the redfield ratio and I shoot for NO3 to be 30ppm and PO4 to be 1ppm. Of course I care about my coral too so I choose softies and LPS that can thrive with such high nutrients.

 

[JayM]

The ratio has no relevance in keeping coral tanks . If your tank is doing well in those parameters, then there is no reason to change anything.

Exactly. I was concerned at first because PO4 is over 10x the "recommended" range, but then I took a deep breath, stepped back to look at the tank and realized that everything is happy and healthy.

That's when I decided that I'm going to watch the numbers, but put more stock into how the tank looks than how the numbers look.

 

[Dburr1014]

Nitrates are over rated, lol.

I used to care but don't see any change since I stopped caring.

 

[Thales]

No longer above .03, why? because anything above will slow down SPS growth. High Nitrates keeps my corals super colorful.

Where did the .3 number come from and hwo was it determined that it slowed down sps growth, and by how much did it slow down? Thanks!

 

[MnFish1]

Balancing the chemical compounds in your reef: Do you pay attention to the nitrate-phosphate balance?

It seems like there used to be a lot more of a focus on the balance between nitrate and phosphate. While the Redfield ratio (comparing carbon, nitrogen, and phosphorus) is occasionally mentioned, it doesn’t appear to be a common point of discussion. When the relationship between nitrate and phosphate is brought up, I have heard ratios of 16:1, 15:1, 10:1, and more. Regardless of what ratio that you use, do you pay attention to the nitrate-phosphate balance in your marine aquarium? Please let us know your experience and any tips that you have to share with the R2R community!

Photo by @youramigojake


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I'm not sure there is much evidence that the Redfield Ratio (or any other ratio) - can predict how well a tank will do, which algae will grow, etc. take this example. (Made up numbers) - Nitrate 160/Phosphate 10 = 16:1 Nitrate 1.6 and phosphate 0.1 is also 16:1 - I'm not sure many people would say they would be equally effective in running a reef tank. Additionally, The Redfield ratio was merely a measure of total N, P, and then C was added - in phytoplankton populations around the world. The surprise was that the ratio was remarkably constant (this has been somewhat changed now). We don't measure total N, or P (or C) in our tanks. here is an interesting article with some of the more recent updates: https://www.nature.com/articles/ngeo2319

 

[shwareefer]

Redfield says 16:1, people I trust say 100:1. I don't think I've ever had either lol, nor do I try.

 

[Fishy888]

There are soooo many variables. Everything capable of using N and P in the ocean uses them in different ratios. I’m pretty certain I read that there are variations even within identical species. Although I am not by any means a marine biologist, I’d be willing to bet that in our tanks the foods we feed and any temperature fluctuations affect the intake of nutrients thus changing average ratio accordingly.

 

[Randy Holmes-Farley]

Redfield says 16:1, people I trust say 100:1. I don't think I've ever had either lol, nor do I try.

Just to be clear, it isn't apparent whether Redfield had ever even heard of reef tanks and he most definitely did not ever claim that ratio was optimal for setting concentrations in a reef tank.

It is simply the ratio of N to P in seawater and in phytoplankton. It was not the result of any sorts of experiments to see where organisms thrive best.

 

[Doctorgori]

I test for both, don’t care about the ratio….I keep phosphate under .5 and don’t really worry over nitrates unless I actually see a issue

 

[JoJosReef]

Nope!

 

[Hans-Werner]

I think the Redfield ratio is one of the moste widely and most severly misunderstood ratios in reef care. The Redfield ratio describes the atomic ratio of C, N and P IN Phytoplankton. It has nothing to do with any ratio in the environment. Between the external concentration and the internal concentration there is the uptake. The uptake is determined by biochemical ion pumps and their kinetics. The usual uptake kinetics in phytoplankton are very close together, lets say uptake starts (= concentration is limiting) at 0.2 µmol/l reactive P, 0.2 µmol/l NH4+ and 0.3 µmol/l NO3-. What does this say about a fixed ratio in the water?

However, scientific studies investigate the ratios of N and P in unpolluted and polluted reefs and find that nitrogen input is most often causing reef decline and a critical N : P ratio is 7 : 1, like in this study from Florida. Specifically nitrate is "bad nitrogen" and harms corals.

When talking about the concentrations necessary for good corals growth, the difference between nutrient limited and nutrient replete concentrations there is a brand new article about tank experiments by Wiedenmann et al. which is very interesting.

 

[Aquariumaddictuk]

I test for both but the ratio doesn't hold any magic for me.
I'm fairly old school & prefer visual indicators.
I've kept discus for a long time & seen owners create problems from testing pH/gh/KH obsessively & reacting with a hair trigger.
Same with corals.
Polyps, algae levels, colours generally let me know if something's amiss

 

[TastyScrants]

Redfield Schmedfield. It’s all about 100:1.

 

[IntrinsicReef]

I think the Redfield ratio is one of the moste widely and most severly misunderstood ratios in reef care. The Redfield ratio describes the atomic ratio of C, N and P IN Phytoplankton. It has nothing to do with any ratio in the environment. Between the external concentration and the internal concentration there is the uptake. The uptake is determined by biochemical ion pumps and their kinetics. The usual uptake kinetics in phytoplankton are very close together, lets say uptake starts (= concentration is limiting) at 0.2 µmol/l reactive P, 0.2 µmol/l NH4+ and 0.3 µmol/l NO3-. What does this say about a fixed ratio in the water?

However, scientific studies investigate the ratios of N and P in unpolluted and polluted reefs and find that nitrogen input is most often causing reef decline and a critical N : P ratio is 7 : 1, like in this study from Florida. Specifically nitrate is "bad nitrogen" and harms corals.

When talking about the concentrations necessary for good corals growth, the difference between nutrient limited and nutrient replete concentrations there is a brand new article about tank experiments by Wiedenmann et al. which is very interesting.

So the coral bleaching that occurs when phosphate becomes limited is the coral consuming it's zooxanthellae?

Or rather, the coral is always consuming it's zooxanthellae at a constant rate, and with nutrient limited conditions the dinoflagellate reproduction can't keep up?

 

[bureau13]

I don't chase a ratio but I do test and compare, since I found out the super-high nitrate problem I'm chasing seems to be paired up with a super low phosphate issue. I've actually been dosing both carbon and phosphate in an attempt to bring the nitrates down but so far it's still not working. Got a thread on here somewhere about that...

 

[Dburr1014]

I think the Redfield ratio is one of the moste widely and most severly misunderstood ratios in reef care. The Redfield ratio describes the atomic ratio of C, N and P IN Phytoplankton. It has nothing to do with any ratio in the environment. Between the external concentration and the internal concentration there is the uptake. The uptake is determined by biochemical ion pumps and their kinetics. The usual uptake kinetics in phytoplankton are very close together, lets say uptake starts (= concentration is limiting) at 0.2 µmol/l reactive P, 0.2 µmol/l NH4+ and 0.3 µmol/l NO3-. What does this say about a fixed ratio in the water?

However, scientific studies investigate the ratios of N and P in unpolluted and polluted reefs and find that nitrogen input is most often causing reef decline and a critical N : P ratio is 7 : 1, like in this study from Florida. Specifically nitrate is "bad nitrogen" and harms corals.

When talking about the concentrations necessary for good corals growth, the difference between nutrient limited and nutrient replete concentrations there is a brand new article about tank experiments by Wiedenmann et al. which is very interesting.

Hans, can you fix the first link?
It's labeled "this study from Florida". I can't get it to work.
I did find the second link interesting.
Thanks!

 

[Superlightman]

I think the Redfield ratio is one of the moste widely and most severly misunderstood ratios in reef care. The Redfield ratio describes the atomic ratio of C, N and P IN Phytoplankton. It has nothing to do with any ratio in the environment. Between the external concentration and the internal concentration there is the uptake. The uptake is determined by biochemical ion pumps and their kinetics. The usual uptake kinetics in phytoplankton are very close together, lets say uptake starts (= concentration is limiting) at 0.2 µmol/l reactive P, 0.2 µmol/l NH4+ and 0.3 µmol/l NO3-. What does this say about a fixed ratio in the water?

However, scientific studies investigate the ratios of N and P in unpolluted and polluted reefs and find that nitrogen input is most often causing reef decline and a critical N : P ratio is 7 : 1, like in this study from Florida. Specifically nitrate is "bad nitrogen" and harms corals.

When talking about the concentrations necessary for good corals growth, the difference between nutrient limited and nutrient replete concentrations there is a brand new article about tank experiments by Wiedenmann et al. which is very interesting.

I unterstand it right deplete experiment was 0.7 nitrate and 0.13 Phosphate and enriched 12 Nitrate and 3 Phosphate? and the second group performed better? 3 Phosphate seems very high

 

[dallast]

I can’t read the dang tests to know for sure! I think it’s time I buy some Hanna checkers!

 

[ReeferSamster]

I've had some of my inhabitants (I consider my OG natural live rock a part of the "inhabitants" along with the fish and corals and invertebrae, through a few decades.

I've had these guys so long over the course of 5 tank upgrades starting with a 10 gallon eventually leading to my Reefer 350, that I developed a spidey sense when I have my daily meditations watching my tank. I stopped testing, feeding or changing water in my tank when I was unemployed for a few months last year. I was not in a good place and I neglected the tank. Fortunately, the live rock was so well established through the years, that they handled the neglected tank, albeit with some problematic algae, which I took care of when my life got back on track.

These days, I 'eyeball' the measurements into a red dixie plastic cup. I know roughly how many squirts of alk or calc i need based on polyp extension and growth rate. Mostly my clam though. He is my canary in the coalmine. He is the first to scream with his gaping exhalant mouth," CHANGE MY WATER YOU LAZY DAD!" (He is a cute hybrid between a Maxima and Deresa clam. He was about 2 inches bit when I got him at Reefapalooza NY from Dr Mac a few years ago. It was the only hybrid there. Dr Mac called it a "Mimosa?" "Meresa?" clam?)

Yes there is a risk. But I've gotten so accustomed to my daily routine and my tank is jam packed with overgrowing corals declaring war on each other, so I can't add anymore corals. (err.well...maybe one more....or two. hehe). It also helps that my nitrate/phophate levels are pretty solid anyway with once or twice (if i'm bored and i have time) water changes per week. Although even though with diligent water changes, I still find that I have to supplement with 2 part slk/calc with balling part c.