phosphate with EI - higher than 3 ppm?

[Happi]

Dear members,

There are plenty of PO4 and GSA threads all over the forums, especially on the TPT where people have GSA along with high PO4 and they still couldn’t figure out why it was happening. As I have explained earlier that GSA has nothing to do with the PO4, but PO4 does alter the water chemistry and it will certainly increase the plant growth if all other nutrients are present at a decent quantity. PO4 have a direct influence on several nutrients in the water, have you ever considered that high PO4 might be interfering with some of the other nutrients that are needed to form GSA, for example Iron, Zinc, Calcium etc.? have you considered that maybe higher Iron could be linked to GSA/GDA and adding more PO4 reduce or eliminate it by precipitating them?

#1, If user is seeing a decrease in GSA after adding more PO4, this suggest that he is reducing or eliminating something in his water that is needed to form GSA. This doesn’t mean that plant are using the higher doses of PO4

#2, if user is also increasing plant mass with additional PO4 which will also reduce the formation of GSA due to faster plant growth. But #1 seems to be playing the major factor.

If someone is convinced that higher PO4 is answer to the GSA and not considering other factors, then am not with those guys. If they are considering the #1 and #2 factor, then I am fully with them. Now am not saying that user is wrong about what he/she is seeing in his tank after adding more PO4, but I hope he/she is also considering other factors as well behind the cause of GSA and its cure.

Plant shouldn’t need more than 3 ppm PO4 weekly but adding say 6-10 ppm will start to do what I have described above. Same could be said for Mg, plant don’t use much but adding more Mg will always reduce several different kinds of algae, particularly GSA/GDA. Water chemistry is the main reason why it works rather than plant needing higher PO4 or Mg. when the water chemistry is correct, neither PO4 or Mg is needed at higher amount to counter these kinds of algae's.

 

[MichaelJ]

Hi @Happi,

I for one appreciate your thoughts on this:

but PO4 does alter the water chemistry and it will certainly increase the plant growth if all other nutrients are present at a decent quantity. PO4 have a direct influence on several nutrients in the water, have you ever considered that high PO4 might be interfering with some of the other nutrients that are needed to form GSA, for example Iron, Zinc, Calcium etc.? have you considered that maybe higher Iron could be linked to GSA/GDA and adding more PO4 reduce or eliminate it by precipitating them?

Yes, that thought had occurred to me, but since I do not see any deficiency issues or ill-side effects (and still no GSA...) by dosing 10ppm weekly in both my tanks I figure why not keep it up... And I am saying that while acknowledging that I had planted tanks without or very little GSA where I hardly dosed PO4...

#1, If user is seeing a decrease in GSA after adding more PO4, this suggest that he is reducing or eliminating something in his water that is needed to form GSA. This doesn’t mean that plant are using the higher doses of PO4

I had already lowered the light intensity a bit beforehand, so its likely a combination of the lower light and the PO4 dosing. I do not know what it is that the PO4 dosing is doing exactly vs. GSA - is it giving the plants the ability to fend them off or is it the GSA that do not thrive with high levels of PO4? Not clear to me. I would assume at 10ppm there are more PO4 available than the plants will possibly need in a low energy tank.

As far as I am concerned I am on the same page as you.

Plant shouldn’t need more than 3 ppm PO4 weekly but adding say 6-10 ppm will start to do what I have described above. Same could be said for Mg, plant don’t use much but adding more Mg will always reduce several different kinds of algae, particularly GSA/GDA. Water chemistry is the main reason why it works rather than plant needing higher PO4 or Mg.

I agree. The PO4 is doing something - altering the water chemistry or whatever the heck... if someone could explain what that something is, then we can make progress. Not before.

when the water chemistry is correct, neither PO4 or Mg is needed at higher amount to counter these kinds of algae's.

Well, thats the big question. What is the right water chemistry then... From reading your post I can't really tell if your for or against adding PO4 or Mg to alleviate these issues, or what your alternative prescription might be? Or if you just want to make people aware that it is not well understood what the excess PO4 or Mg is doing?

Cheers,
Michael

 

[Happi]

Well, thats the big question. What is the right water chemistry then... From reading your post I can't really tell if your for or against adding PO4 or Mg to alleviate these issues, or what your alternative prescription might be? Or if you just want to make people aware that it is not well understood what the excess PO4 or Mg is doing?


Cheers,
Michael

it is quite simple actually, you have to look at it from the chemistry point of view when it comes to Fertilizer in the water. think of a stock solution made with different PH levels and chemicals being used, mixing PO4 and Iron at higher PH usually result in precipitation, EDTA or DTPA chelation usually will prevent this reaction but at some point you will see the precipitation start to occur because both chelate can only do so much for period of time depending on the PH of the solution, while DTPA will hold much longer and prevent the precipitation for longer period compared to EDTA. so PH is playing a quite important role which is directly linked with the KH/CO3 in our aquarium. adding PO4 and Calcium in the solution always formed some kind of precipitation, no matter the PH and no matter what source of chemical I use. PO4 and calcium reaction was only reduced when they were added at very low ppm or if calcium was chelated.

remember the myth about you cannot add PO4 and Iron together in the solution? and this myth still exist even today, its possible to add both together when done correctly. lets say maybe its not a myth, but when it first started, people didn't understand why they were getting precipitation when they added PO4 and Fe together, maybe at that time they didn't understand the role of PH in the solution or water and they were adding them to the higher PH and saw the precipitation and came to conclusion that you cannot have both together at the same time. EI for example follow this approach, where you were told to add PO4 and Fe on separate days. this same logic was applied to this approach and it is true depending on your water parameters, it is certainly true for those who have high KH and PH vs those who have very little KH and low PH, because there is a less precipitation in those waters that have a low PH and KH.

you can perform a simple test to prove this point:
#1 get 500 ml DI water and add 2 gram of KHCO3 and mix until fully dissolve and now add 2 gram of CaNo3 and mix. you will see precipitation immediately forming CaCO3, at this point your solution mainly contain potassium and very little to no calcium.

#2 get 500 ml DI water and add 2 gram of KNO3 and mix until fully dissolve and now add 2 gram of CaNo3 and mix, you will not see any precipitation and K, NO3 and Ca will all be present in the solution.

the point is if someone with a higher PH, KH, high amount of CO3 in their water, they will experience #1 in their aquarium and adding more PO4 might help because some of it will be used by plants while most of it will be precipitated. the user is under the impression that their plant need more PO4 while ignoring the other factor. the same logic apply to all the other nutrients, while some are highly soluble and some are not and user should consider the possibility of precipitation of nutrients rather than relying on one factor. the same apply to Fe and PO4 and now you be the judge that adding 1 ppm of Fe and 10 ppm of PO4 is what the plant are using or they are probably only getting some of each while most of it is precipitated.

those chemicals used as an example in #1 and #2 are just for example, there are many chemicals that will do the same reaction, lets say if you were to add KHCO3 and Cacl, the outcome will be same as #1

people with high KH, PH, CO3 will always have more plant and nutrients related problems compared to those with low PH, KH, CO3. so next time you add 1 ppm Fe or 10 ppm PO4, you are not doing it because plant needs this much, you are doing it because you are under the impression that they need it. your tank water is a bigger version of those stock solution in #1 and #2 and the more CO3, the more Fe, PO4, Ca, Mg etc. you add the more precipitation will occurs. rather than having 1 ppm Fe, 10 ppm PO4, 30 ppm Ca, you probably only have 0.1 ppm Fe, 2 ppm PO4, 20 ppm Ca etc. in the water and these numbers will vary on the scenario. lets assume plant responded well with this approach, but now you are under the impression that your plant need 1 ppm Fe, 10 ppm PO4.

far as the GSA goes and if it gets better after adding more PO4, it is rather responding to these scenarios rather than higher PO4 curing it.

 

[dw1305]

Hi all,

....... PO4 have a direct influence on several nutrients in the water, have you ever considered that high PO4 might be interfering with some of the other nutrients that are needed to form GSA, for example Iron, Zinc, Calcium etc.? have you considered that maybe higher Iron could be linked to GSA/GDA and adding more PO4 reduce or eliminate it by precipitating them?.........

My guess, as well, is that it is an iron (Fe) effect.

This is how <"phosphate strippers"> in waste water treatment (and products like "Rowaphos") work.

cheers Darrel

 

[John q]

Fascinating discussion as always guys.

have you considered that maybe higher Iron could be linked to GSA

My guess, as well, is that it is an iron (Fe) effect.

So finally we have some meat on the bones to chew at.

For the time being lets leave all past arguments aside that iron doesn't cause algae.

I should in theory be able to reverse the effects that I've seen in my tank by simply adding in more Fe.
If I were to leave the dosing regime as is = P04 4.35 ppm, Edta fe 0.45 ppm, Dtpa fe 0.14 ppm, and add in an extra 0.3 ppm of Dtpa fe, do you think this would offset the iron that's being lost due to precipitation?

My tank never fully off gases, ph at it's highest sits around 7.1 and drops to 6.5 at its lowest. Also should mention my tap water is very soft.

Would appreciate whether you think this would help prove or disprove anything, or are there to many variables for this to be of any practical use.

 

[MichaelJ]

it is quite simple actually, you have to look at it from the chemistry point of view when it comes to Fertilizer in the water.

Hi @Happi, Interesting as always and definitely good to know more about the chemical interaction here. So, If the extra PO4 is inducing preciptation such that some other elements (Fe, Ca, and other perhaps) is now available in smaller quantities and the effect of this is that the GSA recedes, wouldn't that suggest then that excess of one or more of said elements is the "cause" or enabler of the GSA opposed to the low PO4 levels initially? Furthermore, If this is a reaction more prone to happen in a higher KH/PH environment, i.e. causing higher percipitation, wouldn't that also suggest that you would experience Fe and possibly other deficiencies? And on the contrary, in a low KH/PH environment you wouldn't see the mitigating effect in GSA of adding the PO4 as you won't have as much precipitation happening? For reference my tanks are currently 1-2 KH and pH around 6.7 - back when I was struggling with the GSA I was probably in the 5-7 KH range and my pH ~7-7.4 (I don't remember for sure).

Besides furthering my own understanding, I am trying to figure out how we can communicate this more succinctly when discussing these matters and offering practical solutions to fellow hobbyists that are struggling with GSA.

Cheers,
Michael

 

[dw1305]

Hi all,
If you have soft water you much less likely to have iron (Fe) deficiency problems and FeEDTA should be suitable as a chelator.

I should in theory be able to reverse the effects that I've seen in my tank by simply adding in more Fe.

Normally that would be true for most elements, but the problem/advantage of iron is that most <"iron compounds are insoluble">, so it is difficult to keep ferric iron ions (Fe+++) in solution, particularly in alkaline, oxidising conditions. This is also why you can <"remove iron ions by oxidation"> etc.

You could continually add a soluble iron compound, like ferric chloride (FeCl3), to hard water, but all those Fe+++ ions will be almost instantly oxidised to insoluble oxides and hydroxides, which is why you need to use a chelator, and a chelator that is suitable for your pH.

cheers Darrel

 

[dw1305]

Hi all,

wouldn't that suggest then that one or more of said elements is the real cause of the GSA opposed to the low PO4 levels initially?

It is back to <"all photosynthetic organisms being "plants">, the major difference is just that higher plants can shuffle (most) nutrients around their cells, while algae are reliant on nutrients (as ions) diffusing through their cell walls.

This difference means that it takes a while in higher plants for <"non-mobile nutrient (like iron (Fe)) deficiencies"> to show, but that isn't true of algae, they can respond to the absence, or availability, of nutrients instantly.

Because phosphate (PO4---) is highly mobile within the plant, a higher plant can continually recycle those atoms to the newest photosynthetic tissue. If PO4--- ions aren't diffusing through the cells of the algae it stops growing, because it can't recycle those phosphorus atoms from another cell.

cheers Darrel

 

[John q]

Thanks @dw1305 will have to get my old chemistry books out and try to dicifer that answer 😀, I guess my experiments will have to be put on ice for now.

 

[MichaelJ]

Hi all,

It is back to <"all photosynthetic organisms being "plants">, the major difference is just that higher plants can shuffle (most) nutrients around their cells, while algae are reliant on nutrients (as ions) diffusing through their cell walls.

This difference means that it takes a while in higher plants for <"non-mobile nutrient (like iron (Fe)) deficiencies"> to show, but that isn't true of algae, they can respond to the absence, or availability, of nutrients instantly.

Because phosphate (PO4---) is highly mobile within the plant, a higher plant can continually recycle those atoms to the newest photosynthetic tissue. If PO4--- ions aren't diffusing through the cells of the algae it stops growing, because it can't recycle those phosphorus atoms from another cell.

cheers Darrel

Thanks Darrel,
Well, I am still angling for a good way to communicate this to the occasional visitor who do not have the patience or interest in the chemistry bit, but just wants those pesky GSA to go away as fast as possible and move along. In addition to the usual suspects (excessive light intensity, poor CO2 application/availability, poor maintenance) I think, for now, I will stick to the advice of increasing PO4 dosing when applicable, but point to this thread for further/deeper information and possibly other cause and effect considerations.

Does that make sense?

Cheers,
Michael

 

[John q]

Well, I am still angling for a good way to communicate this to the occasional visitor

I think we're on a similar page mate. I can only confidently give advice if I've witnessed something with my own eyes, and adding extra P04 with standard doses of ei level fe seems to eliminate GSA. Reducing P04 and fe, in my case, induced gsa.

Why this happens seems to have been discussed for the last seventeen years (probably longer) and nobody appears to have come up with a definitive answer that can be proved or disproved.

I'm under no illusions that my plants consume 4 ppm of P04 weekly, if pressed I'd guess the consumption is 0.5 ~ 1 ppm.

Something is afoot, could it be synergy, interference, higher levels of Po4 in the water column increasing uptake? I don't know and suspect I never will.

 

[si walker]

Today I begun to add extra PO4 on top of my normal Tropica Specialised dose.
I have been trying to keep my tank really clean but losing the battle with the old GSA over the last few weeks. It is really pretty annoying.
Will keep an eye on it for a week or so and slowly increase the dose.
Must admit that I am struggling to decipher some of the info above, so taking what I can and keeping a diary.

Keep you posted. Fins crossed.

Simon.

 

[MichaelJ]

I think we're on a similar page mate. I can only confidently give advice if I've witnessed something with my own eyes, and adding extra P04 with standard doses of ei level fe seems to eliminate GSA. Reducing P04 and fe, in my case, induced gsa.

Hi John, I agree. In my case I don't have the experience with the Fe bit, only the PO4 dosing, except that I can say that whatever the high PO4 is doing, it is not causing any signs of Fe deficiency among my plants either due to the well-known Fe precipitation. So for me at least, giving the advice of tweaking the Fe - or dosing of other elements - to combat GSA that I have zero practical experience with is just not something I can do. If someone can come up with an alternative prescription that works that people can try out, that's a different matter, and I am all for that obviously - that's the whole point of the trouble-shooting part of this forum. A technical conversations about cause and effect of a specific problem is always enjoyful, but in this context of fixing a problem it leads nowhere without an agreeable practical solution to try out.

Cheers,
Michael

 

[dw1305]

Hi all,

In addition to the usual suspects (excessive light intensity, poor CO2 application/availability, poor maintenance) I think, for now, I will stick to the advice of increasing PO4 dosing when applicable, but point to this thread for further/deeper information and possibly other cause and effect considerations.

Does that make sense?

Yes, it does make sense. I don't tend to get <"green encrusting algae"> (or much green algae at all) in the tanks. I don't know why, my guess would be it is some combination of snail grazing, soft water, low nutrients or low light.

The reason I think phosphate addition must work by precipitating out one, or more, of the multivalent cations is just that I can't think how else it could work.

There are some <"specialised higher plants"> that are incredibly efficient at sequestering PO4--- ions and kill themselves by luxury uptake if phosphate is freely available, but again I'd guess that is a much less likely option for GSA.

cheers Darrel

 

[ceg4048]

EI dosing 'full' has 3 ppm phosphate. Is there any point in going higher with phosphate with respect to inhibiting GSA? Calculated out, my weekly added phosphate is currently 2.8 ppm but I've stopped daily dosing EasyCarbo (because I think it's hurting the vallis) and I sense some renewed vigor with the GSA in reponse.

Anyone here doing EI dosing with > 3 ppm phosphate?

GSA is caused by any combination of poor PO4 and poor CO2.
If you are adding the EI target amounts of KH2PO4 then it is unlikely that low PO4 is a factor. One then has to evaluate CO2/flow/distribution.
EasyCarbo=CO2, therefore poor CO2 has to be under immediate suspicion.
If you are only assuming the PO4 content of the water column based on water report or on some factor other than actually adding the prescribed amounts of KH2PO4 then the assumption of the concentration may be flawed.
As usual, flow/distribution are always a candidates.

Cheers,

 

[John q]

If you are adding the EI target amounts of KH2PO4 then it is unlikely that low PO4 is a factor.

Hope you don't mind me drawing you in on this Clive but do you buy the excess iron causes gsa hypothesis. Could it be that the P04 is stripping the water of iron?
Not trying to be smart, genuinely trying to learn things here.

 

[ceg4048]

Hope you don't mind me drawing you in on this Clive but do you buy the excess iron causes gsa hypothesis. Could it be that the P04 is stripping the water of iron?
Not trying to be smart, genuinely trying to learn things here.

Hi John,
No worries mate. I understand that we all are trying to get a grip on cause and effect.
OK, I can see why some may suspect Fe (either in excess or deficiency) since there is a possible issue of Iron Phosphate precipitation. I'm paraphrasing from Barr's conclusion here:
If there is precipitation then the re should be an Fe shortage as well as an PO4 shortage. Micronutrient shortages are not generally correlated with algal blooms. If there is an Fe shortage then the symptoms should show as paleness or yellowing of immature leaves. If there is a precipitation then it should be visible either a clouding of the water or the physical evidence of the precipitate. If these signs are not present then it is unlikely to be an Fe shortage.

Neither is it likely to be an Fe overdose. I have accessed a journal some years ago investigating the Fe concentration level toxic to aquatic plants. I don't have it handy, but I recall the researchers adding up to 13ppm at which point growth of the specimens started to decline. None of the popular algae were present - not GSA, nor hair. Yes, that's 13ppm, not 1.3ppm.
I've used a weekly dosing of up to 2.5ppm with no issues, so I'm confident excess Fe does not cause any type of algae.

In EI dosing, typically, in order to avoid precipitation, PO4 and Fe are dosed on alternate days, so again, if the OP is following this path there should not be any precipitation. I've specifically tested this in very hard water, both using bog standard chelates as well as with more exotic chelates.

Even assuming that there is a precipitation issue, the precipitate falls to the sediment and will be broken down, where the components can be accessed by the plant roots.

As I mentioned many times, micronutrients have that name exactly because the plants only need microscopic amounts, so although there may affect growth performance to some extent if deficient, they will not result in structural decay in the way that macronutrients do. It is the cell death and associated faults associated with necrosis that allow algal spores to bloom. Deterioration of the thin cuticle, for example, exposes the epidermal layer to attack. Micronutrient deficiencies don't cause that level of damage.

Hope this helps.

Cheers,

 

[Andy Pierce]

I'm reading through Walstad's book (early Christmas present) and she says 'Iron's limited availability in oxygenated water sets iron apart from all other plant nutrients. This is because free iron (Fe2+ and Fe3+), which is the only form that algae can use [28], doesn't ordinarily accumulate in the water." (my emphasis) She goes on to say that free iron is generated from iron bound by dissolved organic carbon molecules through photoreduction of iron (e.g. Photoassisted Reduction of Metal Complexes). In contrast, there is evidence (https://www.nature.com/articles/189312a0.pdf) that plant roots can directly take up and use the iron in iron chelates such as EDTA-Fe. So we could construct a theory...

When iron chelates are provided to a planted aquarium, plant roots can directly take up and utilise the chelated iron as an iron source, whilst instead algae must rely on the photoreduction of the chelate to release free iron. When excess phosphate is added, the free iron is precipitated out as insoluble iron phosphate, depriving algae of their iron source, but not affecting rooted plants.​

Is it a real thing? To be supported, there would need to be a meaningful difference in the capacity of 1 ppm phosphate to precipate free iron vs. (in my case) 7 ppm phosphate (or higher). I don't know if that's going to be true. As per usual EI schemes, I dose the chelated iron on days that alternate with the phosphate dosing, which might be about the right timing to remove the free iron resulting from photoreduction of the EDTA-Fe exposed to light on the macro dosing days. I started my increased phosphate experiment on Dec. 7 (Fighting algae with more phosphate - Fireplace aquarium) and didn't change any parameters other than that and as of today there is no evidence of GSA in the tank, but it's too soon to tell. I'll be pretty confident if the tank stays GSA free for an additional two weeks, so I'll report back early in 2022. 😀

[28] Anderson MA and Morel FMM. 1982. The influence of aqueous iron chemistry on the uptake of iron by the coastal diatom Thalassiosira weissflogii. Limno. Oceanogr. 27:789-813

 

[John q]

Hope this helps.

Yes it does, thanks for the comprehensive reply.

 

[Ria95]

I recently had some light growth of GSA on rocks and some plants' leaves. Increased the PO4 by 1ppm and the algae went away. I did not change my iron dosing at all, and when testing at the end of the week it still hits 0.5ppm Fe. Just like before. Not only was there no change in Fe levels, but i doubt that any would consider 0.5ppm Fe limiting for algae.
As others have pointed out, if indeed at the levels we dose PO4 would precipitate the chelated iron compounds, simply reducing the iron dose would make the algae go away. This has not been my experience. Increasing PO4 worked over the years in all types of water. I don't think increasing PO4 is the only possible remediation for GSA in every aquarium, algae are tricky like that. It seems to be working in a majority of conditions so it's worth a try.

Most of the micro fertilizers have chelated iron, often even a mix of EDTA and DTPA. The most common exception from this being Flourish Iron with iron gluconate. In practice the chelated iron forms are stable for a good amount of time at their suitable pH, pH which in most high-tech tanks tends to be on the acidic side. I don't see Fe being so low to not support GSA or plants being an issue when dosing the aquarium according to EI. Unchelated Fe, from FeSO4 for example, will go out of solution rather fast in aquariums. I recall from her posts that Walstad has been dosing FeSO4 as her main source of iron... that explains her notes on Fe and PO4 quickly precipitating in a typical aquarium. The ~20 years since her book has been published have seen many aquariums fertilized with chelated iron that she implies grows algae ( X 2.c). It's normal for knowledge in the hobby to progress as we try new things and resources become more available to the hobby (CO2, fertilizers, soils, TC culture etc).