# Dosing Iron and Phosphate at same time?



## Seattle_Aquarist (Jun 15, 2008)

Hi Hoppy,

Interesting question....got a test tube?


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## Hoppy (Dec 24, 2005)

The easy test would be to use a litre of water, add about 5 ppm of KH2PO4 and about twice that volume of CSM+B, shake it up and test for phosphate. Then let it sit for one day and retest. But, I don't have a phosphate test kit, nor do I want one. I don't know any good way to test the higher concentration that comes with a liquid fert mix. And, this would need to be done with varied pH of the water, since chelators are effective over different pH ranges. I'm hoping someone has already done this.


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## Goldguru (Sep 15, 2016)

Seems iron & other base metals have a high ability to store Phosphates,therefore dosing both @ the same time would only lock your P dose into the minerals?
heavy reading here on mine tailing & P absorbtion.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4546615/
If you can come up with good keywords for searching enter that in upper RH corner of that page to start new query.


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## Hoppy (Dec 24, 2005)

Goldguru said:


> Seems iron & other base metals have a high ability to store Phosphates,therefore dosing both @ the same time would only lock your P dose into the minerals?
> heavy reading here on mine tailing & P absorbtion.
> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4546615/
> If you can come up with good keywords for searching enter that in upper RH corner of that page to start new query.


There is no question that phosphates can combine easily with iron which is not chelated. My question is about the chelated iron, and other metal micros, in trace element mixes, like CSM+B. I believe that bacteria serve the same function as chelators in nature, keeping some iron available to plants. I'm wondering if the reason for not dosing micros and phosphate together is that the common chelators used in trace mixes are not effective over a wide enough pH range to allow that. 

I have no bone to pick with this - I'm just trying to broaden my knowledge base.


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## Immortal1 (Feb 18, 2015)

Hoppy, this is a question I wish I asked a long time ago. For my tanks, I dose PPS-Pro. And with this system (assuming I understand it correctly), I dose XX amount of micros and XX amount of macros EVERY day. I don't remember if there is some time reference between micro and macro dosing, but, in my weekly life I would not have time to wait XX hours between micro and macro dosing. Would seem to me, if PPS Pro is an acceptable system and it includes dosing CSM-B as well as KH2P04, then I can only naively assume the CSM-B chelator will protect the iron from the phosphate. *Can I dose Macro and Micro at the same time?* Yes, simply dose both at the same time into moving water. Text from this site.

Subscribed.


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## Hoppy (Dec 24, 2005)

If we can dose all of our ferts at one time, why can't we make a liquid mix of all of those ferts and only dose that one liquid? Obviously in a liquid mix the concentration of both iron and phosphates is very much higher than in the aquarium water, but with that is a very much higher concentration of the chelator, too. Is it just a "be on the safe side" issue?


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## Redneck tenner (Aug 21, 2016)

Chelated iron forms should be fine. Chelated irons need to be suspended at all times. Agitated. We use a saying called WALE

W. Wettables
A. Agitate
L. Liquids
E. Emulisifade concentrates

Chelated iron most be suspended at all times. Benefits all plant material. Over dose is hard to do. But a temporary blackening effect. 

Sent from my SAMSUNG-SM-G890A using Tapatalk


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## Hoppy (Dec 24, 2005)

Does this mean chelated iron is not dissolved in the water, just in suspension? My mix of water and CSM+B starts out very clear, and remains so for a week or so, then begins to get a bit cloudy. Is that because the bond between chelator and iron cation is being broken?


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## max88 (Jun 22, 2013)

Hoppy said:


> ... Obviously in a liquid mix the concentration of both iron and phosphates is very much higher than in the aquarium water,...


Couple points against mixing and storing them:
1. Chemical reaction runs faster at higher concentration. In the aquarium at lower concentration, the plants still have opportunity to intake before iron and phosphates completely form insoluble substances.
2. When storing liquid mix longer, iron and phosphates can completely form insoluble substances before they are dosed.


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## Immortal1 (Feb 18, 2015)

@max88, your response would explain why dosing is OK, but mixing is not.


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## Hoppy (Dec 24, 2005)

max88 said:


> Couple points against mixing and storing them:
> 1. Chemical reaction runs faster at higher concentration. In the aquarium at lower concentration, the plants still have opportunity to intake before iron and phosphates completely form insoluble substances.
> 2. When storing liquid mix longer, iron and phosphates can completely form insoluble substances before they are dosed.


Therefore, chelators reduce the forming of compounds with phosphate, but don't eliminate them. So, solutions lose bioavailable iron slowly, if the concentrations are low, but much more rapidly with high concentrations.

Another possible factor is that organic compounds - chelators, for example - are not nearly as stable as inorganic compounds, so over time the chelators break down?

Is the color change of my CSM+B + water dosing solution over time, from clear green to cloudy brown, a sign that the chelators are losing their effectiveness? If so, then I need to refrigerate my CSM+B dosing solution, or make less at one time and use it faster.


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## Immortal1 (Feb 18, 2015)

Curious Hoppy, I am mixing around 5 grams CSM+B into 500mL distilled water. This gives me a light brown colored water. I dose 1mL per 10 gallons (same dosing as original PPS-Pro, just less micros).
Near as I can tell the color of the CSM+B mix stays the same until I run out. But then again, I guess I never really paid attention.

Is your mix concentration about the same as mine? Is CSM+B always the same regardless of brand (who you buy it from)? Or is it possible one brand has more / better / different chelators? (I really hope not)


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## citrusvrucht (Mar 1, 2016)

The white cloud you see is just mould, has nothing to do with chelators. You can prevent this by using Nipagin, potassium sorbate,.. 
I mix my own complete fertilizer and use, beside other elements, about 6 gram of potassium phosfate and 12 gram of Fe DTPA and EDDHMA per liter. As long as you keep the chelator intact nothing wil percipitate. I do this by keeping the pH around 4-5, and keeping it dark and cool. Have a control bottle in the fridge for about 2 years now and all is still in solution.
In my dosing pumps I use a mix of macro's on one channel, and micro's with gluconate as one of the Fe chelator on another. If I mix these 2 together I get instant percipitation. 
So dosing phosfate and Iron on the same time had a lot to do with the chelator that is used. A chelator that will break down fast can bind with the phosfate.


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## Redneck tenner (Aug 21, 2016)

Chelated iron in water should darken over time if left alone. Over long periods of time it seperates. Iron has low persistence in all plant material. Hence why its constantly applied and like our algae discussions. We (people) want things super green or certain aquatic plants super red. When in nature often times they are not that green or red. 
Many people including myself have talked about finding and understanding the balance of what a healthy and or natural aquarium is. 


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## max88 (Jun 22, 2013)

Immortal1 said:


> @*max88*, your response would explain why dosing is OK, but mixing is not.





Hoppy said:


> Another possible factor is that organic compounds - chelators, for example - are not nearly as stable as inorganic compounds, so over time the chelators break down?


Someone on this forum posted an analogy regarding phosphates and chelated iron:
Phosphates likes to capture iron. It can easily do so when iron is in pure form. Chelators act as a fortress where iron hides. Phosphates keep bombarding the fortress. Overtime the fortress breaks down, iron is captured, then no longer available to the plants.

So yes, dosing at the same time (at different spots) is OK, mixing and storing together is not. And from reading on this forum, CSM+B solution should be kept in a dark and cool place to slow down chelators break down.


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## Goldguru (Sep 15, 2016)

I would be inclined to say the fortress is more like a tent. 
a minor temporary shield which readily collapses @ the avg users dosing routine.
think of the opposing Army sizes iron to P,then add in the dissolved organics (which are free to bind with what they are attracted to),results in chelated Iron being converted to other compounds and is more or less rendered useless to its claim. (aquarium supplier gimmic?)
a study of US streams showed increase in all micro algae (leading to turbidity of the stream) with rising level of iron @ same P loads,with only P increase there was no apparent change.
Now if the tent only had to deal with a bit of wind(current) and Rain,then that phase of iron may last long enough to be consumed by the plants.

" This may explain the discrepancy in earlier field studies, i.e. differential Fe amounts may generate diverging responses to P enrichment. Here, the P treatment was not significantly different than the control in terms of diazotroph richness and failed to produce the N2 fixer diversity and abundance observed when both P and Fe were plentiful."
article
Iron supply constrains producer communities in stream ecosystems | FEMS Microbiology Ecology

"The stability constant is also affected by the π-bonding strength of the central metal atom (32). It has been shown that, among the transition metal ions, copper has the highest stability. Iron is relatively low: Zn2+ < Cu2+ > Ni2+ > Co2+ > Fe2+ > Mn2+"
article
The chemistry of ferrous bis-glycinate chelate

after looking into this I think I'm going to severly limit the amount of Iron that goes into my tank due to my copper slag substrate was ~ 50% FeO & 30%+ Si02.
Prob why my Diatoms are still going strong.

seems I got a lil off track with some of my links,however the bigger question lies in as to what Iron is in the chelate FeII(ferrous) or FeIII (Ferric).
Wiki goes all over the place with conflicting info on Fe2/3
all articals relating to EDTA (CMB+ active chelating agent) show that FeIII & EDTA only effective to Ph of ~7 
where as FeII appears stable over a larger range of Ph.
FeII-EDTA peak absorption range @ ~ 10 Ph
FeIII-EDTA peak absorption @ ~ 4 Ph

quote from Princeton edu

Like many elements, iron (chemical symbol Fe) can exist in more than one chemical form, or "oxidation state." The two most common forms for iron are Fe(II), in which the iron ion shares two of its electrons, and Fe(III), in which it shares three electrons.

The oxidation state of iron is interesting and important, because it dramatically effects the solubility of iron in sea water. Very long ago, in the earliest days of life on earth, there was little or no oxygen (O2). As a result, iron was most often found in the Fe(II) state. Fe(II) is quite soluble in water, so in those days iron was probably readily available. In those days cyanobacteria, photosynthetic microorganisms responsible for fixing much of the carbon in those early days and, concurrently, manufacturing the earth's oxygen-rich atmosphere, probably had no need for special machinery for harvesting the iron it needed grow, reproduce, and to do this important work. But as atmospheric oxygen increased, iron began to prefer the Fe(III) state, which is quite insoluble in sea water. Acquiring iron then became difficult, and microorganisms began to develop specialized machinery for iron acquisition.

This difference in solubility between Fe(II) and Fe(III) also means that iron acquisition tends to be much more of a problem for aerobic organisms than for anaerobic organisms, since anaerobic environments favor the more soluble Fe(II).

I'm completly confused now as to the pro's or con's of mixing you doses,due to EDTA is in abundance in CMB ~65% so It could also interact with any other metals/compounds present which are not in a soluble present state @ time of dosing.
I do now see your Quandry & I'am kinda wishing & had not looked @ this post LOL
whats more confusing is molar mass of FeII is 71.844 g/mol,and FeIII molar mass is 55.85 g/mol.
but that may explain the forum about pple buying Feii online & 1/2tsp turned thier tanks red..lol


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## roadmaster (Nov 5, 2009)

Hoppy said:


> The easy test would be to use a litre of water, add about 5 ppm of KH2PO4 and about twice that volume of CSM+B, shake it up and test for phosphate. Then let it sit for one day and retest. But, I don't have a phosphate test kit, nor do I want one. I don't know any good way to test the higher concentration that comes with a liquid fert mix. And, this would need to be done with varied pH of the water, since chelators are effective over different pH ranges. I'm hoping someone has already done this.


 Perhaps they have done their testing?, and is why they suggest not to mix the two?
I use macro/micro mix from aquariumfertilizer.com which contain's macro's and micro's (CSM+B) but no phosphate.
I dose this right after water change, and rely mostly on fish food's for phosphate.
I have some KH2PO4 on hand should my feeding's not be enough, but seldom need to use it judging from plant growth I see.
I became more keenly interested in pH and Iron availability in harder water, and have since increased my iron a bit with DTPA I addition to the CSM+B.
I think everyone could test for the phosphates and have wide range of result's due to varying source water's,fish food's,dosing scheme, plant mass,etc.
Might not worry bout Nutrient's much if dosing scheme call's for Daily or every other day dosing.
Might be more critical in low tech with once weekly dosing?


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## Hoppy (Dec 24, 2005)

Back when PMDD was the rage in this hobby people did not dose any phosphate. They began routinely dosing phosphates when they tried it and got much improved, faster plant growth. Most of them quickly found their plants were running short of nitrates, due to the faster plant growth. This eventually led to Tom Barr "standardizing" fertilizing with his estimative index method of fertilizing. I haven't seen anything since then to make me want to stop dosing phosphates. Actually, I haven't seen anything to make me want to stop using the EI method.

But, I have always been curious about the warnings not to dose phosphates and iron at the same time. As I learned more about what chelators are, and how they work, I found I couldn't reconcile the value of chelators with the warnings not to mix phosphates and iron, so I started this discussion. Apparently this, like so much in this hobby, is a complicated subject with no simple, cast in stone answers.

It's nice to know that there is an endless backlog of information to be learned about this hobby.


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## citrusvrucht (Mar 1, 2016)

Goldguru said:


> seems I got a lil off track with some of my links,however the bigger question lies in as to what Iron is in the chelate FeII(ferrous) or FeIII (Ferric).
> Wiki goes all over the place with conflicting info on Fe2/3
> all articals relating to EDTA (CMB+ active chelating agent) show that FeIII & EDTA only effective to Ph of ~7
> where as FeII appears stable over a larger range of Ph.
> ...


If you are able to make an Fe2+ chelate and dose it in your aquarium with normal oxygen levels, the Fe2+ state won't last long and will turn into Fe3+ pretty quick. I will have to look up the exact time, but if I remember correctly it was about max 30min. 

Here is a chart with the stability constants of various metals. Overall Fe3+ has the highest Kstab. 









The influence of phosphate on NON chelated iron:


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## Andy0x1 (Mar 4, 2016)

Hoppy said:


> Back when PMDD was the rage in this hobby people did not dose any phosphate. They began routinely dosing phosphates when they tried it and got much improved, faster plant growth. Most of them quickly found their plants were running short of nitrates, due to the faster plant growth. This eventually led to Tom Barr "standardizing" fertilizing with his estimative index method of fertilizing. I haven't seen anything since then to make me want to stop dosing phosphates. Actually, I haven't seen anything to make me want to stop using the EI method.
> 
> But, I have always been curious about the warnings not to dose phosphates and iron at the same time. As I learned more about what chelators are, and how they work, I found I couldn't reconcile the value of chelators with the warnings not to mix phosphates and iron, so I started this discussion. Apparently this, like so much in this hobby, is a complicated subject with no simple, cast in stone answers.
> 
> It's nice to know that there is an endless backlog of information to be learned about this hobby.



I came across this thread because I can't figure out why my phosphate crashes to 0 PPM a few hours after dosing it.

I recently purchased a dosing pump so I could dose Phosphate ~350mg 3x a day on top of the NPK+Mg mix that is also dosed 3x a day resulting in (6) spaced out doses during the photoperiod. (50 gal tank.)

Plants are showing Phosphate deficiency symptoms which makes sense since the test kit suggests the same.

I feel like I'm the only person with this problem.


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