How useful are nitrate and phosphate test readings?

[JayM]

Looks like a healthy young reef. Thanks for sharing

Fingers crossed it stays that way. Pretty steep learning curve after being out of the hobby for 30ish years. Especially because there isn’t a “right” way to do it.

 

[Dan_P]

TLDR: Please post a picture of your reef and include your nitrate and phosphate measurements.

-After doing thousands of tests for nitrate and phosphate over the last 20+ years on many different systems, I am still confused. I have seen tanks with undetectable NO3 and PO4 grow hair algae before my eyes. I have seen systems with 40ppm nitrate and .3ppm phosphate without a speck of algae and growing healthy coral. I just can't seem to find the pattern. New hobbyists are told to watch and manage these numbers, but we can't seem to decide what they should be. I'm beginning to think we are having the wrong conversation.

-It seems like algae and coral are utilizing these nutrients ( ammonium? some other form of phosphorus?) before they form into the compounds we are testing for. There is also an organic pool of these nutrients that we can't test for. It just seems like what we test for is a very small part of the picture.

-After many decades of hobbyists sharing test results of the world's reef tanks, I feel we should have dialed in an ideal nutrient profile. Maybe one doesn't exist. Which goes back to my point of "Why are we telling new hobbyists to concern themselves with these numbers?" Almost every time I see a person with an algae problem, the first question is "What are your nitrate and phosphate levels?" Then they get hit with a barrage of conflicting advice on what these levels should be.

-There has been talk of a "golden ratio" of nitrogen to phosphorus. Whether it is Mike Paletta observing many successful tanks at 100 to 1, or the Redfield ratio of 16-1. These ratios are often touted as responsible for specific algae/ cyano growth, as well as coral health. I have followed the 100-1 ratio for years and had success, but I have had success with other ratios. Again, I don't see a pattern (other than having more nitrogen than phosphorus in general).

-In recent years, targeting higher nutrient levels and dosing is popular for coral coloration and health. But some people find success with low nutrients and feeding their coral. Do zooxanthellae require inorganic nitrogen/phosphorus/potassium dissolved in water like terrestrial plants or can they be sated by feeding their host? Can we have low nutrient systems where the majority of nutrients are consumed by bacteria and these bacteria feed the corals? I feel like all of these are possible scenarios and are currently practiced.

-So, please post your tank and your test results. I want to see outliers like Richard Ross and whoever is the opposite low nutrient extreme. And if you know of any literature that answers these questions, please drop a link.

I was thinking about replying to the notion that nitrate and phosphate levels don’t seem to correlate to algae growth issues, but then I thought about advice we receive on R2R. So, a philosophical digression.

Let me propose that that information obtained on social media should be treated just like that obtained from the current versions of AI chat bots. The information can be badly flawed, though it can also be pretty good. You just can’t tell. Humans like AI are trained on data sets which can be biased, flawed, and incomplete. Humans like chat bots are programmed to put together information to explain things. If the information is flawed, the synthesized explanation can be nonsense. Conclusion: you should not be only using social media to understand very complex systems like an aquarium.

 

[IntrinsicReef]

I was thinking about replying to the notion that nitrate and phosphate levels don’t seem to correlate to algae growth issues, but then I thought about advice we receive on R2R. So, a philosophical digression.

Let me propose that that information obtained on social media should be treated just like that obtained from the current versions of AI chat bots. The information can be badly flawed, though it can also be pretty good. You just can’t tell. Humans like AI are trained on data sets which can be biased, flawed, and incomplete. Humans like chat bots are programmed to put together information to explain things. If the information is flawed, the synthesized explanation can be nonsense. Conclusion: you should not be only using social media to understand very complex systems like an aquarium.

Please do reply to the idea that nitrate and phosphate don't seem to correlate to algae growth issues. Discussing this topic with the community was the whole point of my questions.
I think I see what you are saying with the AI digression. I understand that not everyone will give accurate information( test results) associated with their system. I think though that mass anecdotal evidence has been helpful for the hobby as well as detrimental.

 

[Randy Holmes-Farley]

Please do reply to the idea that nitrate and phosphate do not seem to correlate to algae growth issues. Discussing this topic with the community was the whole point of my questions.
I think I see what you are saying with the AI digression. I understand that not everyone will give accurate information( test results) associated with their system. I think though that mass anecdotal evidence has been helpful for the hobby as well as detrimental.

Above a certain limiting level of nitrate and phosphate, more does not make algae grow faster. Like gas in a car, gas allows it to go, but it dies not go faster with more gas and dies not stop unless gas is very low.

That limiting level is likely to be low enough to also begin to limit many corals, and is likely below recommended ranges.

0.03 ppm phosphate and a few ppm nitrate is sufficient for algae growth.

 

[Dan_P]

Like gas in a car, gas allows it to go, but it dies not go faster with more gas and dies not stop unless gas is very low.

Been meaning to discuss this notion with you for some time.

Every algae is covered in a static boundary layer, the thickness varies. Algae may also be part of a biofilm or in some physical arrangement where there is resistance to diffusion in addition to the boundary layer. In such a scenario, a higher concentration of nitrate or phosphate would increase the diffusion rate and allow faster nutrient uptake and possibly faster growth, though only to a limit because CO2, O2 and other waste diffusion would remain the same. This would be particularly important for macro algae like GHA with a more limited surface area then pelagic micro algae.

Thoughts?

 

[IntrinsicReef]

Above a certain limiting level of nitrate and phosphate, more does not make algae grow faster. Like gas in a car, gas allows it to go, but it dies not go faster with more gas and dies not stop unless gas is very low.

That limiting level is likely to be low enough to also begin to limit many corals, and is likely below recommended ranges.

0.03 ppm phosphate and a few ppm nitrate is sufficient for algae growth.

Thank you. That is a great explanation and analogy.

 

[Randy Holmes-Farley]

Been meaning to discuss this notion with you for some time.

Every algae is covered in a static boundary layer, the thickness varies. Algae may also be part of a biofilm or in some physical arrangement where there is resistance to diffusion in addition to the boundary layer. In such a scenario, a higher concentration of nitrate or phosphate would increase the diffusion rate and allow faster nutrient uptake and possibly faster growth, though only to a limit because CO2, O2 and other waste diffusion would remain the same. This would be particularly important for macro algae like GHA with a more limited surface area then pelagic micro algae.

Thoughts?

I don’t know, but these things are presumably already baked into limitation studies of particular organisms, though I can see how it might vary tank to tank.

this paper seems to find either N or P limitation and raising the other usually has no effect.

Wayback Machine

 

[Garf]

Here’s something else,

The effect of nutrient enrichment on the growth, nucleic acid concentrations, and elemental stoichiometry of coral reef macroalgae

The growth rate hypothesis (GRH) links growth rates with organism elemental stoichiometry. Support for the GRH was found for many animal species, but less so for plants. This is the first study to test the GRH in macroalgae. Tropical coral reef macroalgae ...

www.ncbi.nlm.nih.gov

 

[IntrinsicReef]

Here’s something else,

The effect of nutrient enrichment on the growth, nucleic acid concentrations, and elemental stoichiometry of coral reef macroalgae

The growth rate hypothesis (GRH) links growth rates with organism elemental stoichiometry. Support for the GRH was found for many animal species, but less so for plants. This is the first study to test the GRH in macroalgae. Tropical coral reef macroalgae ...

www.ncbi.nlm.nih.gov

Fantastic article, thank you. Definitely some findings I did not expect. "Despite the increases in RNA and P tissue concentrations, growth rates were reduced in the P-fertilized treatment in all three species relative to control (Fig. 5). Therefore, our results do not directly support the growth rate hypothesis, for which correlations among P, RNA, and growth are expected"
Very interesting that the algae stores the phosphorus instead of utilizing it for increased growth. But that make evolutionary sense for an organism in nutrient poor waters with waves of nutrient upwellings or runoff.

 

[Reef.]

That said, in established tanks with an abundance of coral, the coral seems to outcompete the algae for nutrients, and algae is less likely to grow.

A bigger factor is the algae has less room to take ahold with an abundance of coral.

 

[Dan_P]

I don’t know, but these things are presumably already baked into limitation studies of particular organisms, though I can see how it might vary tank to tank.

this paper seems to find either N or P limitation and raising the other usually has no effect.

Wayback Machine

Just now read the abstract and therein lies one explanation for macro algae growth, and possibly every other nuisance algae in an aquarium, in low nutrient water: the sediment is the source. I would go further for aquaria and add all surfaces as a possible local nutrient source.

With relatively low flow in aquaria, surface accumulation of organic matter should be large and thick relative to nuisance algae size. For green hair algae, rhizomes would be embedded in this rich source. Bacteria growth and the release of inorganic nutrients such as ammonia, phosphate and vitamins from it completes the explanation for patchy thick growth of pests in nutrient depleted water found in aquaria.

 

[jda]

I have no doubt that if algae is attached to aragonite then it could find a pretty large reservoir nearby. The plant could absorb some local po4 and the rocks will locally unbind more to equilibrium.

If you are speaking of the greyish/brown sludge that might be in surface and in the rocks, all evidence that i have seen indicated that it is mostly inert having been scavenged for anything of use already. However, this could be less true in tanks where full ecosystems are not yet established and there is not microfauna to scavenge the stuff.

 

[Jmp998]

I tried for a long time to keep nitrate and phosphate low, and my tank suffered for it.

Now I let the tank stay where it is happy-about 0.1 phosphate and 10 nitrate-and mostly don’t fight it. Less algae and happier corals.

However I still test every 1-2 weeks and when I make any significant changes In feeding, stocking, etc to make sure I am not drifting too much. Although I don’t think the exact level is important, some corals including my Gonioporas do not like changes in nitrate and phosphate especially any rapid drop in phosphate.

 

[IntrinsicReef]

A bigger factor is the algae has less room to take ahold with an abundance of coral.

I definitely agree that less real estate on the rocks doesn't give the algae the space to take hold. The shading of rocks from corals is also important. However, I think that fast growing coral outcompete algae for desirable nutrients ( they have algae living inside of them after all). In tanks with a large coral population, bare rock under intense light can remain algae free for long periods of time. There might be other reasons for this, but I think that coral can outcompete algae just as a macroalgae scrubber can.

 

[IntrinsicReef]

I tried for a long time to keep nitrate and phosphate low, and my tank suffered for it.

Now I let the tank stay where it is happy-about 0.1 phosphate and 10 nitrate-and mostly don’t fight it. Less algae and happier corals.

However I still test every 1-2 weeks and when I make any significant changes In feeding, stocking, etc to make sure I am not drifting too much. Although I don’t think the exact level is important, some corals including my Gonioporas do not like changes in nitrate and phosphate especially any rapid drop in phosphate.

Yes. It is looking to me like testing NO3 and PO4 for algae control doesn't mean much. I have seen algae grow under the range of low range test kits, and over a certain threshold, I'm told it grows at a near constant rate. Testing for coral health seems more important, but coral can also seem to adapt to a wide range.

 

[apb03]

I think Nitrate and Phosphates alone only tell a part of the story. I tested this morning at 55 nitrate and 0.11 phosphate and I do not have any algae in my display. I do, however, have coralline covering the majority of my rock exposed to light. I believe without the coralline and my herbivores my tank would be an algae-filled mess.

I have a QT tank that I don't perform much upkeep on and recently I had to move several rocks from my DT there due to a zoa issue I had. The existing rocks are covered in GHA while the rocks from my DT remained clean. That tank has nothing but a couple of snails in it and algae is covering the other rocks, so to me, it's less about nutrients and more about tank maturity and herbivores.

 

[Garf]

Yes. It is looking to me like testing NO3 and PO4 for algae control doesn't mean much. I have seen algae grow under the range of low range test kits, and over a certain threshold, I'm told it grows at a near constant rate. Testing for coral health seems more important, but coral can also seem to adapt to a wide range.

Algae growth has always been herbivore related to me. My previous softy tank with tangs had no visible algae but in the sump where I had a waterfall scrubber, well, algae went bonkers. I also did a submerged horizontal screen that became populated with amphipods, munching their way through it until it grew coralline.

howdy from the uk - day one

thought i would chip in and let you comment on my effort so far. Backgroung of display- 5 x 2 x 2 with 240 ltr sump containing skimmer (massively inefficient), DSB in display (silica play sand), approx 100 kgs live rock. Most corals are 7 years old and all fish but 2 of the tangs, are of...

algaescrubber.net

 

[jda]

I would not compare micro to macro algae in most ways - probably like comparing modern birds to dinosaurs. The two types of algae do not really act much alike even though they share some common ancestors and base characteristics.

Scrubbers work because the algae has no predators in that area - same with a fuge. True bare rock is a magnet for algae - like dry/dead rock. True live rock without corals on it is rarely bare and has coralline, fauna, matting and film bacteria, etc. that can evict dinos and hair algae before they get settled.

Algae = vacant lots and no CUC. I am glad that some of you have fish that are helpful, but I never seem to find them.

 

[EricR]

I was thinking about replying to the notion that nitrate and phosphate levels don’t seem to correlate to algae growth issues, but then I thought about advice we receive on R2R. So, a philosophical digression.

Let me propose that that information obtained on social media should be treated just like that obtained from the current versions of AI chat bots. The information can be badly flawed, though it can also be pretty good. You just can’t tell. Humans like AI are trained on data sets which can be biased, flawed, and incomplete. Humans like chat bots are programmed to put together information to explain things. If the information is flawed, the synthesized explanation can be nonsense. Conclusion: you should not be only using social media to understand very complex systems like an aquarium.

I agree with your philosophical digression.
For some of us, fortunately or unfortunately, the Internet is often the most easily-accessible source of information (good or bad).

 

[jda]

The internet is perhaps the most easily accessible source for maybe data and opinions. The internet also has some information and knowledge, but this is harder to find. Books are still probably best for information and knowledge, but there are books available online.

1. Data - almost worthless, but you have to have it - too many wrongly see data as having too much value
2. Information - good, takes data, but also humans who know what they are doing
3. Knowledge - best, takes knowledge from a modicum of folks both supporting and challenging each other

What makes it so tough with reefing is that opinons and anecdotes are a lot of what we have to go with since there is so little actual good science done with regard to the hobby... so whose opinions that you choose to trust is paramount. The good thing is that the books written in the 70s, 80s and 90s are still good since biology and chemistry have not changed in our lifetimes - just ignore the specific equipment references (although some are still good).

In this case, important to see D/I/K for what they are. In a lot of these studies, what comes out of them might be knowledge for the ocean, or some lab environment, but they need to be downgraded for people with reef tanks... maybe even as far as just raw data (or maybe information if you are lucky). The best can do this - some of them post on here, so good to pay attention when they do.