How useful are nitrate and phosphate test readings?

[jda]

Seen some papers that hosts want poly/meta phosphates, not ortho. They can store meta/poly for later use and also use the other things bound to meta/poly compound export junk from the host. It appears that hosts will also use ortho, but not if poly/meta are around. Hosts also prefer to get organically bound P before using po4 too. Have seen some very recent studies that show that 3 ppb of po4 is not growth limiting to any organism and something like .05 can start to growth limit some corals (in a bad way) but not even close to all - this does not even account for the other sources of phosphorous that things have access to.

I would strongly suggest that you break your nutrients down into 4 parts... sugars and building blocks vs available and residual. You are in control of sugar content with lighting quality and quantity. You are also in control of available building blocks by feeding your fish more. Even if residual building blocks (otherwise known as waste products are low), nothing in your tank will be limited if you keep the available sources up.

You have probably seen me post this many time, but my po4 is about 1-3 ppb on Hannah Ultra Low. Stuff grows like crazy, but I feed my fish like crazy and there is no chance that anything is starved for phosphorous. Saying that corals suffer with low po4 is likely misstated or only part of the story... like carbon dosing, using media or cutting back on feeding was also likely involved.

Those bacteria that you are growing with the OC will need more than N and P. They will need other traces too. Just think about the harm that growing more bacteria could cause and not just the potential benefit - nobody has good info or knowledge on all of this since it has never really been studied, but all of the anecdoctes and experiences seem to point to lower no3 as the only tried-and-true benefit.

 

[IntrinsicReef]

They will need other traces too. Just think about the harm that growing more bacteria could cause and not just the potential benefit - nobody has good info or knowledge on all of this since it has never really been studied,

I have run many systems with and without carbon dosing over the last 20 years. I have have heard the theory of growing and giving bad bacteria a boost( where is @Timfish I'm sure he has some interesting points to add). I honestly haven't seen the carbon dosing make a difference in coral diseases or other negatives. My experience with carbon dosing is that it is an effective tool for bacteria to out compete algae. I am not sure chemically how bacteria outcompetes algae but I have noticed this effect even in freshwater tanks. I have noticed many more filter feeding sponges and worms in carbon dosed tanks. I am more recently experimenting with carbon dosing for feeding coral.

 

[jda]

Did you notice the increased bacteria feeding the coral when you have done this in the past? I think that you might already know what you are going to see this time...

 

[Ziggy17]

I don't know that 5 or 10% margin of error is a reason not to test. If you are new to the hobby I would suggest testing parameters to make your own comparisons with your system health. Testing calcium and the buffer system is very important in reef tanks. A calcium reading that is 360 or 440 instead of the actual 400ppm is still very useful. Tracking trends is especially important. My questions posed on this thread are based on successful reef tanks having widely varying nitrogen and phosphorus readings. These can be 50x to even 100x in extreme examples, not a few percent difference.

I think you missed the point of my reply, but that’s ok.

 

[Dan_P]

Right. And even long- dead coralline can look the same. Coralline grown on rock or glass slides still looks essentially the same even if you let it dry for weeks+.

Excellent. I did not think coralline faded that easily but I had no evidence to back up that conjecture.

 

[jda]

Fresh and growing coralline is a bit more rough, is hard but you can put a fingernail into it and it scrapes easier. It is also where the urchins hang out to eat. You don't see algae growing in this stuff... or at least I never have. There is plenty of purple stuff in the tank that is not alive - including dead (or maybe dormant) coralline.

 

[IntrinsicReef]

Did you notice the increased bacteria feeding the coral when you have done this in the past? I think that you might already know what you are going to see this time...

I saw many filter feeders thriving that I don't normally see in reef tanks without carbon dosing. I mostly carbon dosed on client tanks for algae control and didn't pay much attention to the relationship between feeding bacteria and feeding coral. I have have an acropora dominated system at home that I recently started carbon dosing. So, I will be able to observe the changes close while only changing the one thing.

 

[Randy Holmes-Farley]

So I’ve read all the same stuff most have in terms of “ideal“ water parameters, and I’m guilty of buying in to them as well. But unless you have a chloromiter (sp) that costs a few grand or much more, how can we know what the water parameters actually are, given the margin of error with every test kit on the market. If the MOE is between 5-10% from most kits and you’re running tight nutes, your NO3 and PO4 could be awesome or non existent. I know we get ICP tests done, but do most write down our checker results when we pull the water for the ICP test and contrast? If they match, was it a fluke given the MOE for our home tests? It just seems that until be get super accurate home tests available to us, we are chasing a ghost (numbers), when really the livestock and nuisances should be the indicator of good water.
BTW, I’m new to the hobby and open and welcome criticism to my POV.

zig.

On a side note, what is the chemical
structure in your avatar?

 

[taricha]

A question I feel pertinent to this discussion would be whether corals receive the majority of their N&P requirements from their nutritional sources or is a significant portion gained through their own mechanisms for uptake? I feed my fish it poops and my coral eats DOCs from which it gets it N&P. Conversely I feed my fish, it poops and my corals takes in preferred Nitrogen and phosphorus from the water column.

This may be too broad "corals" to give a meaningful answer. All our corals by definition do both. But even within "SPS", I think there's going to be too much variation to say that each coral receives X amount from inorganic uptake from water, and Y amount from ingested cells of phyto/bacteria.
My personal hunch is that the hobby has selected for those strains of corals that are better at getting what they need from light and inorganics in the water, and we mostly killed off a bunch of types that were more dependent on planktonic cells for nutrition.
Also, I don't think N & P should be thought of here interchangeably. Or at least do so carefully.
I think there are many ways even without eating cells of bacteria/phyto that a coral can get plenty of N in a system with no detectable NO3. (ammonia, proteins, aminos, maybe even N-fixation?)
There aren't as many forms of P that won't raise your testable PO4 for you to play such games as easily with P. When my water tests as having near-undetectable PO4, my corals act like they are P starved. Target feeding Phyto and carbon dosing didn't change that for me. So there are some limits to the argument that corals can just get P from eating stuff if there's not PO4 in the water. Though in some systems, (JDA) that certainly seems to happen.

Another example I feed my bacteria carbon, they pull Nitrogen and phosphorus from water column, then my coral eats bacteria. From this it would seem I should focus on the N&P needs of the bacteria not so much the corals.

am curious if zooxanthellae needs to absorb nitrogen and phosphorus from the water column or it can fulfill those needs by sharing the nutrients their coral host eats.

This recent paper @Lasse shared had an interesting angle relative to this discussion.

Interesting reports according Darwin's Paradox

Since my beginning as reefer and holding corals I always has said that it would be very strange from a biological energy conservation point of view if not the coral animal eat and digest at least a part of the algal residents in their tissue. Many has understand that the coral animal must in one...

www.reef2reef.com

Nature article itself:
https://www.nature.com/articles/s41586-023-06442-5

Basically, they showed that a bunch of corals we keep can grow just fine on PO4 and NO3 alone. They stripped all particulates going into the coral system by UV and filtration. And the corals grew well, and of course the corals with no NO3/PO4 are the saddest looking things ever.
The researches went through a lot of effort to show that what was happening was that the coral symbiont algae grew and multiplied on the NO3/PO4, and the corals ate their internal symbiont cells to grow the colony.

"Here we show, through a series of long-term experiments, that the uptake of dissolved inorganic nitrogen and phosphorus by the symbionts alone is sufficient to sustain rapid coral growth. Next, considering the nitrogen and phosphorus budgets of host and symbionts, we identify that these nutrients are gathered through symbiont ‘farming’ and are translocated to the host by digestion of excess symbiont cells."

Also see figure 1 for cool pics of the sad/happy corals.

 

[MnFish1]

This may be too broad "corals" to give a meaningful answer. All our corals by definition do both. But even within "SPS", I think there's going to be too much variation to say that each coral receives X amount from inorganic uptake from water, and Y amount from ingested cells of phyto/bacteria.
My personal hunch is that the hobby has selected for those strains of corals that are better at getting what they need from light and inorganics in the water, and we mostly killed off a bunch of types that were more dependent on planktonic cells for nutrition.
Also, I don't think N & P should be thought of here interchangeably. Or at least do so carefully.
I think there are many ways even without eating cells of bacteria/phyto that a coral can get plenty of N in a system with no detectable NO3. (ammonia, proteins, aminos, maybe even N-fixation?)
There aren't as many forms of P that won't raise your testable PO4 for you to play such games as easily with P. When my water tests as having near-undetectable PO4, my corals act like they are P starved. Target feeding Phyto and carbon dosing didn't change that for me. So there are some limits to the argument that corals can just get P from eating stuff if there's not PO4 in the water. Though in some systems, (JDA) that certainly seems to happen.




This recent paper @Lasse shared had an interesting angle relative to this discussion.

Interesting reports according Darwin's Paradox

Since my beginning as reefer and holding corals I always has said that it would be very strange from a biological energy conservation point of view if not the coral animal eat and digest at least a part of the algal residents in their tissue. Many has understand that the coral animal must in one...

www.reef2reef.com

Nature article itself:
https://www.nature.com/articles/s41586-023-06442-5

Basically, they showed that a bunch of corals we keep can grow just fine on PO4 and NO3 alone. They stripped all particulates going into the coral system by UV and filtration. And the corals grew well, and of course the corals with no NO3/PO4 are the saddest looking things ever.
The researches went through a lot of effort to show that what was happening was that the coral symbionts grew and multiplied on the NO3/PO4, and the corals ate their internal symbiont cells to grow the colony.

"Here we show, through a series of long-term experiments, that the uptake of dissolved inorganic nitrogen and phosphorus by the symbionts alone is sufficient to sustain rapid coral growth. Next, considering the nitrogen and phosphorus budgets of host and symbionts, we identify that these nutrients are gathered through symbiont ‘farming’ and are translocated to the host by digestion of excess symbiont cells."

Also see figure 1 for cool pics of the sad/happy corals.

Agreed - it's too broad a topic to make a blanket statement.

 

[jda]

I wanted to add that if people want to read or study this, then corals means true coral, or stonies that leave skeletons AND are photosynthetic to most researchers and scientists. Softies are identified more by name or common class like colonial polyps, sinularia, anenome, etc. - these are truly not coral to most of the scientific community. NPS are usually identified as NPS. However, you will find something that does not follow this model, so you have to find the clues and stuff.

There are very few studies that span true coral types - they either completely focus on SPS or LPS. Sometimes if you find a study by an aquarium, oceanographic institute, or other org with a wide breath of focus on all types of corals and softies, they will include a paragraph or two about how their findings might/not apply to other types.

If anybody wants to see the difference between available types of phosphorous and just po4, Hach makes a total P test kit. They are around $100. I got a partial set a while back and when I used it, my total P was 4-10x the amount of po4 (varied by day and stuff). In my heavily fed system, the total P is about 6x what the po4 is... which nobody would say is "low" or anything. Most of this was like poly/meta phosphates... which I learned from an accident experiment break down in about three days to ortho. I went to grab it a few months ago for a thread similar to this and it was out.

 

[MnFish1]

I wanted to add that if people want to read or study this, then corals means true coral, or stonies that leave skeletons AND are photosynthetic to most researchers and scientists. Softies are identified more by name or common class like colonial polyps, sinularia, anenome, etc. - these are truly not coral to most of the scientific community. NPS are usually identified as NPS. However, you will find something that does not follow this model, so you have to find the clues and stuff.

There are very few studies that span true coral types - they either completely focus on SPS or LPS. Sometimes if you find a study by an aquarium, oceanographic institute, or other org with a wide breath of focus on all types of corals and softies, they will include a paragraph or two about how their findings might/not apply to other types.

If anybody wants to see the difference between available types of phosphorous and just po4, Hach makes a total P test kit. They are around $100. I got a partial set a while back and when I used it, my total P was 4-10x the amount of po4 (varied by day and stuff). In my heavily fed system, the total P is about 6x what the po4 is... which nobody would say is "low" or anything. Most of this was like poly/meta phosphates... which I learned from an accident experiment break down in about three days to ortho. I went to grab it a few months ago for a thread similar to this and it was out.

My question - in our tanks is such a test needed - or even meaningful. IMHO - no

 

[IntrinsicReef]

Right. And even long- dead coralline can look the same. Coralline grown on rock or glass slides still looks essentially the same even if you let it dry for weeks+.

It agree it can dry out and retain the purple coloration. Although, it can die and turn white as well. I think my point is that the water conditions that favor stony coral growth ( good mineral balance especially) and herbivores grazing soft algae are more important for unimpeded coralline growth, rather than it's natural ability to fend off other algae.

 

[MnFish1]

It agree it can dry out and retain the purple coloration. Although, it can die and turn white as well. I think my point is that the water conditions that favor stony coral growth ( good mineral balance especially) and herbivores grazing soft algae are more important for unimpeded coralline growth, rather than it's natural ability to fend off other algae.

First long-dead corralline CAN look the same - but often dead corralline is white. I'm not sure what the other posters expertise with coralline is -but I have had 3 issues where the tank died - the coralline also died - it was not pink. I think this is a mistake

 

[jda]

My question - in our tanks is such a test needed - or even meaningful. IMHO - no

Not any more useful than an orthophosphate test. If you think that your tank is phosphorous limited only because ortho tests low, then it might be interesting to see what the total P is. These other forms appear just as meaningful as ortho according to some studies. This might be a good idea before people dose orthophosphate. If we knew a good ratio of total P to po4, this could also change our advice on when/how/why to dose phosphates at all... like maybe better to dose a few forms of poly instead of ortho.

BTW - Lasse posts a lot of great stuff. Anybody interested in this stuff should read these and then follow the references in those articles. Some of the studies are in other languages, so translate them and do the best that you can - in some of these instances they can mix terms that we are used to and can add in other terms like "complex phosphate" which takes you a bit to figure out means poly. I have read a few where I could never tell if they mean nitrate or nitrogen, so I had to give up, but most of them are really good.

 

[taricha]

If anybody wants to see the difference between available types of phosphorous and just po4, Hach makes a total P test kit. They are around $100. I got a partial set a while back and when I used it, my total P was 4-10x the amount of po4 (varied by day and stuff). In my heavily fed system, the total P is about 6x what the po4 is... which nobody would say is "low" or anything.

what sorts of numbers did you get for total vs PO4?

I've got a similar kit by hanna. One day when I get bored I might check my water and water from a LFS in town.

 

[jda]

Like 1-3 ppb on Hannah ULR and between 6 to 30 on the Hach (converted). The Hach just converts all forms of P into ortho and then does acetic acid. Nobody would think that 6 to 30 is low... even though some think that 1 to 3 is low.

I just looked and cannot find the Hach that I had. They have colorimeters now - probably really good. My price above is likely to be totally off... sorry.

 

[Ziggy17]

On a side note, what is the chemical
structure in your avatar?

Hi Randy,

thanks for noticing. It’s a caffeine molecule. We own/operate a coffee truck as a side hustle and that’s our logo. our actual logo has (caffeine) underneath the molecule. When people see our truck, there is little to no confusion as to what drug we’re dealing

 

[Randy Holmes-Farley]

Hi Randy,

thanks for noticing. It’s a caffeine molecule. We own/operate a coffee truck as a side hustle and that’s our logo. our actual logo has (caffeine) underneath the molecule. When people see our truck, there is little to no confusion as to what drug we’re dealing

Nice! The nitrogen’s not showing were confusing me.

. This is caffeine, for those interested;

 

[IntrinsicReef]

My personal hunch is that the hobby has selected for those strains of corals that are better at getting what they need from light and inorganics in the water, and we mostly killed off a bunch of types that were more dependent on planktonic cells for nutrition.

I think this is an important statement. We have imported a variety of different corals over the years and I tend to see many of the same ones do well in people's aquariums. The survival rate for aquacultured coral and wild corals is quite different in my experience. Even maricultured corals often don't make the long-term adjustment to our reef tanks.