Optimal phosphate level? (Mixed Reef)

[TexasReefer82]

In our home reefs there are a bit different views of how corals grow.
@Hanswerner and others have shown how coral sceleton growth is affected by lack of nickel and zink. These elements affect how brittle or dense a coral sceleton will be and the length between branching.
Circulation does affect this too.
In the last few years we have noticed that a slight pH increase from CO2 scrubbers will make the corals more dense.
I have customers that has birdsnest corals that halfed their branch length from the moment the CO2 scrubber was installed.

That's really interesting, can you link to the paper about zinc and nickel?

 

[Stigigemla]

There is an article of @Hanswerner and coautors that was published in Koralle (Coral magazine Germany) some years ago. It was a link to it here on R2R a year or 2 ago.

 

[TexasReefer82]

Calcification itself was not inhibited but the skeleton was more porous, in line what what I’ve mentioned above. Overall calcification is higher but skeletons can be up to 17% more porous. This is arguably an issue in wild reefs but not in our tanks.

I'd have liked to see them measure "skeletal mass increase" over this period instead of branch elongation. I think that mass increase more truly measures calcification and is independent of variable density. I don't think we can safely assume that the branch elongation can be used as a perfect proxy for calcification.

 

[TexasReefer82]

I think there are two different discussions occurring in this thread:
1) What N/P ratio is ideal for our tanks?
2) should we run elevated levels (above NSW) of either N or P (even if they're in the perfect ratio)?

I think the papers presented in this thread make a compelling case for the right N/P ratio being that which occurs on healthy wild reefs: 5-7.

The second question has a couple considerations that i can think of. There are reasons that an elevated level of these nutrients (still in the ideal atomic ratio) would be practical: to avoid the inaccuracy of testing errors that occur at very low concentrations that may be at or below the LOD of our hobbyist test kits; also to avoid deficiency of either due to variable/increasing consumption by our growing corals over time.


Some follow-up questions I'd have on this topic:

- Do our tanks suffer from P deficiency? And if so how would we recognize this? What are the symptoms of this in our tanks?

- If the top N/P ratio limit is 22 then what's the bottom? Corals need N as well and surely it can't go too low without adverse effects. Also, are there limits on the absolute concentrations of either N or P independently? Surely even in the perfect atomic ratio P can be too high and N can be too low.

- Are there any examples of wild reefs that have elevated absolute levels of NO3 and PO4 (e.g. 1ppmNO3 and 0.2ppm PO4) but that are still in the Proper N/P ratio (7.66) - and how are these reefs doing?

- What if I simply dose both NO3 and PO4 to my tank with a N/P ratio of 5 to 7? Would this constitute perfectly balanced nutrition? ...similar to the way that we dose Calcium and alkalinity together in a stoichiometric proportion. How much of either N or P am I adding to the tank every time I feed the fish or coral?

I'd love to hear everyone's thoughts.

 

[jda]

If you dose N, then you are likely only contributing to the residual levels in your tank. Remember that most corals want to get their nitrogen from ammonia/ammonium and not from nitrate. Having a higher level of N by feeding fish means that you had ammoni[a,um] along the way. Adding to the back end likely does nothing. It costs the coral between 30-50% more energy to use no3 as it does to use ammonia/ammonium.

When you dose P, you are mostly just adding to the bound reservoir in the aragonite. This will likely become a problem in the future.

Regardless of if you think that it is a good idea to have higher N and P levels, the best thing is to very likely feed the fish a lot more and let it go through the cycle instead of adding it on the back end.

I don't think that you can just look at a backend ratio and get this right since it was the "process" that benefited the coral and not the resulting residual levels that show up on a test kit. ...sorry if this does not make sense. This gets us back to the age-old paradigm that always works - heavy import and heavy export. However, this does not work for a lot of people because they lack the second-level experience and thinking to know when they get there... there is no test kit or "number" that they can go off of... it just takes time and experience.

I don't post this too much since it seems like it is a losing battle, but we should call N and P "building blocks" and not "nutrients." They are technically a nutrient since it is defined as "a substance that provides nourishment essential for growth and the maintenance of life" but they do not act like food that most people think of when they think of nutrients. Heck, under this definition, then the lunch that I had today is a coral nutrient since I am needed personally for the growth and maintenance of the life in my tank. That definition is too broad just like "coral" is too broad when people want to compare. N and P are needed to build new tissue and to repair old. Most corals can recycle inside their tissue for repair. Death SHOULD NOT occur when N and P are limiting, just limited growth - so people who claim to have seen death probably have something else going on. N and P are needed to build, not to live - they are not sugars or "food" which are necessary to live.

 

[TexasReefer82]

"most corals want to get their nitrogen from ammonia/ammonium and not from nitrate. Having a higher level of N by feeding fish means that you had ammoni[a,um] along the way."

This is a good point.

I completely understand that N and P along with Calcium, bicarbonate, Magnesium, and all the trace elements provide zero caloric value to the coral, only building blocks. When I say Nutrients wrt coral I'm referring to N and P.

"Death SHOULD NOT occur when N and P are limiting, just growth" I think you mean to say not death but LACK of growth should occur with limited N and P.

 

[jda]

Yes. There are growth limiting levels when low, but they are called "growth limiting" and not "messenger of death." I edited the post since I still could. :(

 

[Scrubber_steve]

1) What N/P ratio is ideal for our tanks?

Create a concept & reality leaves the room.

Some follow-up questions I'd have on this topic:
- Do our tanks suffer from P deficiency? And if so how would we recognize this? What are the symptoms of this in our tanks?

Phosphate In The Reef Aquarium: By Randy Holmes-Farley

I think the papers presented in this thread make a compelling case for the right N/P ratio being that which occurs on healthy wild reefs: 5-7.

So you are answering your own question (2)– “should we run elevated levels (above NSW) of either N or P (even if they're in the perfect ratio)?”
If you believe what occurs on healthy wild reefs is ideal for your aquarium then tune your NO3 to 0.031ppm & your PO4 to .0095 ppm. They are the parameters quoted in one of the papers for NSW.
If you run those values a low P-N ratio will become important because P will be below the "threshold"..

- If the top N/P ratio limit is 22 then what's the bottom?

The N-P ratio upper limit isn’t 22:1.

The paper states-

1. " We exposed corals to imbalanced N-P ratios in long-term experiments and found that the undersupply of phosphate severely disturbed the symbiosis, indicated by the loss of coral biomass, malfunctioning of algal photosynthesis and bleaching of the corals."

2. "In our experiments, a phosphate concentration of ~ 0.3 μM (0.0285 ppm) at a N/P ratio of >>>> 22:1 <<<<< yielded an overall healthy phenotype."

3. *** "Accordingly, it is likely that the absolute N/P ratio becomes also less critical for the proper functioning of the symbionts when phosphate concentrations exceed a vital supply threshold > 0.3 μM (0.0285 ppm), even when the symbionts are rapidly proliferating."
=======================================

{In their experiments} the N-P ratio was critical when P value was below the "threshold". Above this "threshold" the N-P ratio is unimportant.

To put this in context, consider an aquarium run at - N = 2 ppm & P = 0.04 ppm. This is a P-N ratio of 50:1

Somewhat interesting is 'their' threshold value for PO4 of 0.0285 ppm. Compare that to the PO4 value given for NSW (.0095 ppm) given in the other paper.

 

[Stigigemla]

A sudden large decrease in the phosphate level can cause tissue loss on corals. Montipora digitata seems to be among the most sensitive for this. But if the value sink slowly they just dont grow much.

 

[Lithoman]

Okay I give.. you super minds lost me.. The OP asked what was the Optimal Phosphate Level..
I would like to know that as well.. plenty of debate here, which is a great thing.. If you could state what levels
of P and N you are running successfully, then state your scientific reasons..... That could help us newbies hopefully find our sweet spot.
Cheers!

 

[special-ops-s2k]

Interesting read! Thanks for posting all those articles

 

[TexasReefer82]

Okay I give.. you super minds lost me.. The OP asked what was the Optimal Phosphate Level..
I would like to know that as well.. plenty of debate here, which is a great thing.. If you could state what levels
of P and N you are running successfully, then state your scientific reasons..... That could help us newbies hopefully find our sweet spot.
Cheers!

Hahaha, we certainly did get sidetracked.

In short, you won't find any consensus or scientific proof of any ideal phosphate level for corals kept in aquaria (I'm sure some will disagree :)).

If you aimed to maintain Nitrate at ~5ppm and Phosphate at ~0.05-0.1 ppm your corals would do fine (some will disagree).

Ultimately, pick a starting point and hold it for a couple months, observe your corals, and make changes as necessary. Every system is different.

 

[Scrubber_steve]

.

Thanx for that Like dear.

 

[Superlightman]

Interesting thread. For my experience when I had high nitrate around 25 and high phosphate between 0,16-0,25, the soft corals growth good ,lps seem normal but the acroporas near not grow at all and I had little alk and near no calcium consumption.Every time my phosphate level went under 0,1 the alk and calcium consumption started again. This show me that the coral growth is better with less phosphate at least in the skeleton.An with phosphate over 0,2 I couldn't keep some acroporas ,some systematically died.
The euphyllias never seemed to be different in a high or low level, but anecdotally when my levels were high when I moved one euphyllia,it breaked completely,the skeleton was the same as porcelain, maybe it was because of the phosphate?

 

[DDenny]

Wow I just read the entire thread. Very interesting and at some points makes since. My phosphates are at .013 nitrates at 2ppm. So way over the 22:1 more like 153:1 so I need to lower the nitrates to reduce that ratio or bring up phosphates a little. Since I don't have fish that means feeding the corals and Reef Roids will probably be the best for accomplishing this. Just started feeding this week so going with a small dose target feeding mainly since I only have three corals at the moment. going to start feeding 1/5 the recommended dose targeting corals and see what that does to the phosphates.

 

[pbrown]

If we played guess the po4 level?? You wouldn't like the answer. I guarantee whatever the results the decimal point would be insignificant. Lol

Goals…

 

[sssky]

It's less about your absolute phosphate level and more about your N/P ratio. Current reefs (real world reefs) that are maintaining very fast growth have an N/P of 4-5x.

Anything under 10-14x will be great. Over 20x is when you see less growth.

If we're talking absolute values, a study concerning the impact of phosphates levels on acropora revealed acropora grew the most with the greatest polyp extension at the highest phosphate level of .5. While corals will grow significantly faster under higher phosphate levels, it comes at the expense of a slightly more porous skeleton.

New advances in coral research have revealed that high nitrate levels, especially in relation to phosphate levels, are very detrimental to coral skeletal growth and polyp extension. High phosphate levels, especially in relation to high nitrate levels, led to significantly increased coral growth, calcification, and polyp extension.

The levels for their low nitrate/high phosphate conditions were LN/HP = ~ 0.06 μM NO3−/~3.6 μM PO4−; N / P ratio = 1

https://appliedecology.cals.ncsu.ed...-growth-nitrogen-impairs-but-phosphorus-aids/
https://www.nature.com/articles/srep31768
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5441187/
https://www.researchgate.net/public...a_muricata_A_controlled_experimental_approach

God dangit..... you copied "LN/HP = ~ 0.06 μM NO3−/~3.6 μM PO4−; N / P ratio = 1" and it drove me insane trying to figure out why N/P ratio is 1. It appears you copied 3 letter less. It is 1:60......

Otherwise thank you so much for sharing this. It is such an eye opener.

 

[Batusay]

I prepared this table to summarize the results of the Euphyllia paper and also to convert all the values into ppm so that we can compare to our own systems. An interesting note is that the paper mentions that 0.3uM or 0.028ppm PO4 is approximately the critical threshold above which excess NO3 is not detrimental.

Beneath the values from the paper I listed the values of some tanks that I know personally as well as the values of some contributors to this thread: jda and glennf. All these tank grow very happy acropora with wildly different nutrient levels. Amazingly, every hobbyist tank listed maintains PO4 at or above the critical threshold - except for jda who maintains an N:p ratio of approximately 20, which is also consistent with what the paper states is a healthy ratio. So perhaps there are indeed multiple ways to grow the coral.

The next question I have is exactly the same as jda's: what's the value of raising nitrate to 25 with a phosphate of 0.1? Would nitrate at 0.5ppm work just as well while also giving a more favorable Nitrogen limited ratio? I'll say this about the display tank at my local reef store - it's fantastic! Their acropora specimens are the epitome of health. No one can see that tank and say that 25NO3/0.1PO4 is bad for coral. However, they also blast it with light, 900 PAR at the top of the rocks, and they admit that with nutrients that high the PAR is necessary to bring out the colors otherwise they're just brown. Jda, the lighting consists of 3x400 Radiums plus 6xRadion fixtures (not sure which generation but it's probably the latest, knowing them).

higher nutrients - higher PAR?; lower nutrients - lower PAR? all as long as the N/P ratio is within a healthy range and critical thresholds are met???

Great job, thanks! It would be great to specify the type of light source (led,t5,MH), the intensity in the upper third of the tank, the severity of the fish load (as suggested by member jda)

 

[Randy Holmes-Farley Verified Community Expert]

Otherwise thank you so much for sharing this. It is such an eye opener.

I know this is old, but I don’t want to let it stand unchallenged. I actually disagree and do not consider the N/P ratio important. There’s no data that says it is. Targeting both N and P independently is a better way to go, IMO.

Here’s my recommendation:

https://www.reef2reef.com/ams/randy’s-thoughts-on-nutrient-target-ranges.1087/
4. What targets seem reasonable? Of course, that depends on all the other factors at play, such as types of corals, availability of ammonia, particulate foods, etc. However, for a mature mixed reef, this would be how I personally would run it:

• Let nitrate float between 5 ppm and 50 ppm. I’d use gentle export in this range, such as growing macroalgae.
• Above 50 ppm, I’d begin to focus more on reducing it, by organic carbon dosing, turf or macroalgae, etc.
• Below 5 ppm, I’d begin to dose ammonia or feed more. The target level might drop lower if dosing ammonia, just like the heavy in/heavy out scenario where nitrate may not be as needed.
• Let phosphate float between about 0.06 ppm and 0.3 ppm. This range is higher than I’ve recommended in the past. I’d use gentle export in this range, such as growing macroalgae.
• Above about 0.3 ppm, I’d begin to focus more on reducing it, by turf or macroalgae, or a binder such as GFO or lanthanum (has its own risks to tangs). If a binder: GO SLOW. Turf and macroalgae will typically be slow enough.
• Below 0.06 ppm, I’d begin to dose sodium phosphate or feed more to get the level up.

 

[Superlightman]

I know this is old, but I don’t want to let it stand unchallenged. I actually disagree and do not consider the N/P ratio important. There’s no data that says it is. Targeting both N and P independently is a better way to go, IMO.

Here’s my recommendation:

https://www.reef2reef.com/ams/randy’s-thoughts-on-nutrient-target-ranges.1087/
4. What targets seem reasonable? Of course, that depends on all the other factors at play, such as types of corals, availability of ammonia, particulate foods, etc. However, for a mature mixed reef, this would be how I personally would run it:

• Let nitrate float between 5 ppm and 50 ppm. I’d use gentle export in this range, such as growing macroalgae.
• Above 50 ppm, I’d begin to focus more on reducing it, by organic carbon dosing, turf or macroalgae, etc.
• Below 5 ppm, I’d begin to dose ammonia or feed more. The target level might drop lower if dosing ammonia, just like the heavy in/heavy out scenario where nitrate may not be as needed.
• Let phosphate float between about 0.06 ppm and 0.3 ppm. This range is higher than I’ve recommended in the past. I’d use gentle export in this range, such as growing macroalgae.
• Above about 0.3 ppm, I’d begin to focus more on reducing it, by turf or macroalgae, or a binder such as GFO or lanthanum (has its own risks to tangs). If a binder: GO SLOW. Turf and macroalgae will typically be slow enough.
• Below 0.06 ppm, I’d begin to dose sodium phosphate or feed more to get the level up.

0,3 phosphate is high are you sure? over 0,15 in general my kh goes down and over 0,2 some sps said good bye to me in the past when others seems to like it