Nitrates and phosphates - what does the latest science say?

[jda]

Phosphate binds to aragonite in a reversible bind to the equilibrium in the outside water. If new calcium carbonate grows over the old structure, then the phosphate is locked in until the structure is "melted."

Aragonite can bind large amounts of phosphate many, many times more than in the water column. Dr. Holmes-Farley says that it binds in an exponential fashion where it will bind more with higher concentrations in the water.

Even in my tank with .01 phosphate, if we soaked some of the sand in a small volume of fresh saltwater, it would read out with quite a high number.

Most of the time, the aragonite binds this stuff once it is dead and not so much while it is living. I have tested fresh acro skeletons and they release very little phosphate, even in small concentrations of water. I also tested some large-size ARM and they had just a trace of phosphate in 1l of water at 15 ppb (0.000068 ppm in a 180G tank).

 

[jda]

Phosphate and nitrate impact on growth appears to be different for each individual coral and algae. While coralline with grow with slightly elevated numbers, with NSW(ish) paramters, I can cover the front glass in purple every two weeks and can grow coralline so fast on tunze powerheads that they can get plugged solid. It is annoying. The stuff will not grow even close to this fast with say 2-3 nitrate and .1 phosphate, but it will still grow and make most people happy.

You can also grow acropora skeletons so fast that the tissue cannot keep up and the tips get burnt. People who do this keep the alk low so that the calcification is growth-limited by the alk content.

I have other corals that would not mind N and P at even higher levels. I am not sure that my clams would care as long as they were under .5 and 20/30. In the typical mixed reef, I doubt that people could tell if the building blocks were elevated. In an acropora only reef, then you probably could.

Color can be different. I only keep acropora and if I let the N and P levels rise, I get deeper, darker color that tends to shift to monochromatic with less contrast. With NSW(ish) parameters, I get whiter whites, more contrast and sharper, brighter colors. To each their own on this and some corals look better in monochrome with higher N and P (red plant) and some look better with more contrast and brighter colors. Growth is significantly better with NSW(ish) parameters so if you like to see the different colored tips of actively growing acropora, then this might be for you.

 

[Belgian Anthias]

Phosphate binds to aragonite in a reversible bind to the equilibrium in the outside water. If new calcium carbonate grows over the old structure, then the phosphate is locked in until the structure is "melted."

Aragonite can bind large amounts of phosphate many, many times more than in the water column. Dr. Holmes-Farley says that it binds in an exponential fashion where it will bind more with higher concentrations in the water.

Even in my tank with .01 phosphate, if we soaked some of the sand in a small volume of fresh saltwater, it would read out with quite a high number.

Most of the time, the aragonite binds this stuff once it is dead and not so much while it is living. I have tested fresh acro skeletons and they release very little phosphate, even in small concentrations of water. I also tested some large-size ARM and they had just a trace of phosphate in 1l of water at 15 ppb (0.000068 ppm in a 180G tank).

Did you test the acro skeletons content and or the increase of P in the water column? When a biofilm grows on aragonite the biofilm will dissolve it, use minerals and nutrients released by the aragonite, and release what is not consumed.
To test the release of P and N over time I think one should wait at least two weeks and use water containing a known amount of nutrients enough to support initial growth of a biofilm. When the biofilm dies off it will release its content to be recycled and reused.
To know the content of coarse one has to dissolve it.

 

[anit77]

A lot of these tests and anecdotal results from reefers revolve around more mature systems with a larger coral biomass and the biggest system of all, the ocean. Even the BRS videos on the 160 and their recent ones at WWC you see a large amount of coral added early on after the system startup. Much more so than the average hobbyist when starting up a new system. Everything in life is about balance and that, obviously, includes all the organisms we put in our boxes of water, no matter how big or how small, coral included. When I see the OP's tank in the vid I also see a sizable coral mass as well. Look at how much food WWC is putting in their tanks a day! I bet with half or a third of the coral in there those tanks would be full of GHA, Cyano and who knows what else. Even @revhtree tree has seen his share of problems with his new tank.

Just as P's latching to the substrate increases exponentially with the increase in P levels, the uptake of that P increases exponentially as the biomass increases. I'm beginning to believe that adding a lot more coral early on after cycling is advantageous to the health of the system. Maybe even so far as to matching x amount of coral mass per fish added to the system. I just don't seem to see this topic talked about or at least I haven't stumbled across it.

It would be really nice to see BRS @randyBRS do some testing with some new system startups and how a slower approach to adding coral effects to over all "Health" of the systems. If a min ratio of fish/cuc to coral mass can be established it could go a long way to helping new reefers start their journey in the hobby. Not only that but it could help those having issues by just adding more coral. Think setting up systems designed to plow right through the ugly phase, all with no denitrators, reactors filled with GFO or carbon dosing. More successful new reefers equals more people staying in the hobby.

I know there's a lot more to it than that, but it's a place to start looking at this aspect of reefing differently just as we're talking about higher N & P now.

 

[randyBRS]

A lot of these tests and anecdotal results from reefers revolve around more mature systems with a larger coral biomass and the biggest system of all, the ocean. Even the BRS videos on the 160 and their recent ones at WWC you see a large amount of coral added early on after the system startup. Much more so than the average hobbyist when starting up a new system. Everything in life is about balance and that, obviously, includes all the organisms we put in our boxes of water, no matter how big or how small, coral included. When I see the OP's tank in the vid I also see a sizable coral mass as well. Look at how much food WWC is putting in their tanks a day! I bet with half or a third of the coral in there those tanks would be full of GHA, Cyano and who knows what else. Even @revhtree tree has seen his share of problems with his new tank.Just as P's latching to the substrate increases exponentially with the increase in P levels, the uptake of that P increases exponentially as the biomass increases. I'm beginning to believe that adding a lot more coral early on after cycling is advantageous to the health of the system. Maybe even so far as to matching x amount of coral mass per fish added to the system. I just don't seem to see this topic talked about or at least I haven't stumbled across it.It would be really nice to see BRS @randyBRS do some testing with some new system startups and how a slower approach to adding coral effects to over all "Health" of the systems. If a min ratio of fish/cuc to coral mass can be established it could go a long way to helping new reefers start their journey in the hobby. Not only that but it could help those having issues by just adding more coral. Think setting up systems designed to plow right through the ugly phase, all with no denitrators, reactors filled with GFO or carbon dosing. More successful new reefers equals more people staying in the hobby.I know there's a lot more to it than that, but it's a place to start looking at this aspect of reefing differently just as we're now talking about higher N & P now.

Perfect segue into today's BRStv episode. The concepts and thought processes that Ryan share about N/P are really bringing this conversation to the forefront and likely changing the way we think about them. I'll have it posted in a bit But yes, there's much more experimenting and testing to be done about these parameters!

 

[anit77]

Perfect segue into today's BRStv episode. The concepts and thought processes that Ryan share about N/P are really bringing this conversation to the forefront and likely changing the way we think about them. I'll have it posted in a bit But yes, there's much more experimenting and testing to be done about these parameters!

Awesome, glad to hear you guys are ahead of the game!

Look forward to watching the new episode.

 

[jda]

Did you test the acro skeletons content and or the increase of P in the water column? When a biofilm grows on aragonite the biofilm will dissolve it, use minerals and nutrients released by the aragonite, and release what is not consumed.
To test the release of P and N over time I think one should wait at least two weeks and use water containing a known amount of nutrients enough to support initial growth of a biofilm. When the biofilm dies off it will release its content to be recycled and reused.
To know the content of coarse one has to dissolve it.

You do not have to dissolve it. The aragonite on the surface will release P back into the water without any kind of biological help. This can happen pretty quickly. The aragonite structure on the inside takes more time, but it can release too if the structure is porous.

I can test no appreciable phosphate from either ARM or Reborn - both dead coral skeletons. It is certainly getting dissolved.

 

[Ashish Patel]

I was running lower nutrients as so many people say SPS will brown out otherwise, I feel this is false because everyones system is different and we should be doing what your tank need and can handle in terms of nutrient uptake. I don't believe the ocean is low nutrients at all with its constantly changing nutrient levels has alot of room for error. Nutrients in a new tank with dry rock should not try and follow advice on a nutrients of an established reef with mature colonies. Few months back my phosphates was 0.00 to 0.04 range (for 1+ year) and after I had my son I was away from the house and coming back every 3 days to feed the tank frozen foods and dose aminos and such, Scared of the tank not having enough food I would dump food (pellets, LRS, acropower, reefroids, etc) in the system. 1 week later my Alk had dropped from 7.9 to 7.1dkh. I was constantly having to increase my alk dosing and decided to just focus on testing Alk 2-3 times per week on my visits to the tnak. Anyways last week after not testing Phosphate and NO for 2-3 months I was shocked.. Phosphates where 0.28 and Nitrates where above 10PPM. My cheato in the refugium just disappeared, perhaps the cyano on the sand bed had something to do with that. I feel my tank is healthier at higher phosphates so reluctant to bring it down now.

 

[Brew12]

I don't believe the ocean is low nutrients at all

Completely agree with this. If you pull all the algae eaters off a reef it will quickly become overrun with algae. Just because a system has low measurable nutrients in the water does not make it a low nutrient system. There are massive amounts of nutrients being both released and consumed on a reef.

 

[jda]

This is all true. It is also true that water brought back from the coral sea, Caribbean and Hawaii show 1 PPB of phosphate on a Hannah test kit (sometimes zero, sometimes two). This matches up with RHF's articles on seawater parameters. This lends legitimacy to the notion that "throughput" with heavy import and heavy export is where it is at, and not residual numbers in the water column grabbed by a test kit.

 

[anit77]

This is all true. It is also true that water brought back from the coral sea, Caribbean and Hawaii show 1 PPB of phosphate on a Hannah test kit (sometimes zero, sometimes two). This matches up with RHF's articles on seawater parameters. This lends legitimacy to the notion that "throughput" with heavy import and heavy export is where it is at, and not residual numbers in the water column grabbed by a test kit.

In our closed systems the higher organism waste and uneaten food decays into a fixed water column. In the ocean it is ether swept away by the current or sinks to the bottom and directly onto coral. I would wonder what the P number would look like during a storm or when there's a current shift where deep water is pushed over the reef when there's a high turbidity level. Hard to do in practice but interesting to know none the less.

 

[jda]

Detritus is benign of P (usually). Dr. Holmes-Farley has shown evidence that nearly all phosphate is excreted in urine. Most other foods and detritus are scavenged by bacteria in hours leaving not much behind - nature is good at this. I do not know if a storm would raise P levels at all, but it might stir up some detritus and bring in some outside water with who-knows what. Keep in mind that big storms are incredibly hard on reefs.

The other variable in the wild is "coral food." When we were in the coral sea, the local biologist said that these shallow reefs had nearly no planktonic feeding of acropora (water was too clean), but some of the atolls and other parts of the ocean did especially where there was run-off. Sun provided the food through zoox and sugars, which is enough.

 

[TexasTodd]

Anyone else read the article on rats vs bird population on islands in the new Coral that just came out? Introduced rats eat birds, eggs, baby birds. It essentially says that islands without rats, have many times the number of seabirds. Seabird guano runs off into the water and the fish and coral populations around islands with lots of birds, are at a much higher density.

 

[Ashish Patel]

Completely agree with this. If you pull all the algae eaters off a reef it will quickly become overrun with algae. Just because a system has low measurable nutrients in the water does not make it a low nutrient system. There are massive amounts of nutrients being both released and consumed on a reef.

This is a good point and 100% true.

 

[Belgian Anthias]

You do not have to dissolve it. The aragonite on the surface will release P back into the water without any kind of biological help. This can happen pretty quickly. The aragonite structure on the inside takes more time, but it can release too if the structure is porous.

I can test no appreciable phosphate from either ARM or Reborn - both dead coral skeletons. It is certainly getting dissolved.

I do not think aragonite and or calcite will dissolve much in seawater without any help. If it does I think we have a problem on the reef.
What is measured, without any action of a third party, is what is leaked, not the content. Erosion helps as the particles become available in the water column, available to be colonized .
In a marine aquarium the aragonite sand and rock is meanly dissolved by the acids produced by bacterial activity on its surface. This way the total content is released. For phosphate it may be estimated to be +- 0,2% of the dissolved weight. A lot is used up by the processes in the active biofilm growing on the media. Aragonite based rock or shell and certainly calcite based rock and shell may not dissolve in seawater. (Without the production of acids and or lowering the pH on its surface)?
ARM is a processed form of calcium carbonate, not the natural thing from the sea.

As is claimed P release will happen without any help and it may happen very quickly, this observation is important. I would like to know where this information comes from.

 

[Belgian Anthias]

Just because a system has low measurable nutrients in the water does not make it a low nutrient system. There are massive amounts of nutrients being both released and consumed on a reef.

I agree!

 

[ReefGeezer]

So, I have a couple of critical thinking questions... Is bioavailable N & P somehow less available at low but detectable levels than it is at higher levels? Is the mere presence of inorganic N & P evidence of suitable levels to support the systems chemical and biological processes because otherwise wouldn't they have consumed/bound/oxidized beyond detection?

 

[Belgian Anthias]

What may be overlooked is the fact that in a mixed reef with a relative high bio-load a lot of nutrients are processed daily. Maintaining a low nutrient level in a system with a high daily demand , an unbalance may be created when for some reason the daily supply is interrupted. In a closed system nutrients may be depleted, the bio- system may be starved, chains broken.
In nature the levels may be very low but the supply is unlimited.
Preserving existing reserves considering the daily needs seems a safe way of working. Better as to relay on conflicting reports about the growth of corals in the ocean. The persistence of naturally occurring values in a mixed reef aquarium is something I would not consider. For A little more or less coral growth!?

 

[CoralWealth]

following along

 

[Scrubber_steve]

So, I have a couple of critical thinking questions... Is bioavailable N & P somehow less available at low but detectable levels than it is at higher levels? Is the mere presence of inorganic N & P evidence of suitable levels to support the systems chemical and biological processes because otherwise wouldn't they have consumed/bound/oxidized beyond detection?

Yes, you could say, if at any time your NO3 at its lowest was 5ppm you have an excess of 4.9ppm.