# EDTA Iron and UV Sterilizer Experiment / Conclusion?



## unirdna (Jan 22, 2004)

All the anecdotal evidence re: whether or not UV sterilizers "kill" chelated iron pushed me to the point of doing my own experiment.

It all started when I recently rescaped my 46g tank. I removed a wall of pearlgrass, did a water change, and added iron to the tank. Hours later, the tank water became hazy. We discuss this at the bottom of page 16 of my 46g journal thread. I figured it was either a small bacteria bloom or maybe the beginning of "green water".

It went away a day later, and I stopped thinking about it. 

I further rescaped my tank a week or two later; removing more biomass (a hairgrass carpet this time). Again, I finished with a water change and a dose of iron. And again, I got a day's worth of hazy water. When testing my water params, I noticed that iron was dropping off immediately after dosing.
And just like last time, the hazy water was gone in a day or so.

I needed to know what was causing this brief time of hazey water.

So, I stirred up my substrate a bit (to simulate a "rescaping") and did a water change. This time I did not add iron..... Waited..... NO HAZE!

HMMMMMM

So after a day or two, I dosed the tank to .25ppm iron (Kent Proplant) without any disturbance, and without any water changes. A few hours later - BAM - hazy water.

So, adding iron to my tank creates hazy water that lasts for about 24 hours, and clears up around the same time my iron tests read 0ppm.

Too interesting. Had to try the next obvious test. I have been running a UVS on my tank since 2 months after it was set up. I bought it to fight off the greenwater my tank had taken on. It did a wonderful job; so I just let it run as a preventive measure against GW and fish disease.

If you run a query using "unirdna" and "UV Sterilizer", you'll see a plethora of theads I've piped in on, singing the praises of the UVS.

....I'm starting to have 2nd thoughts. Here's why.

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I turned off the UVS (coralife TT 9w), and again dosed .25ppm iron. A few hours later, no hazy water. 24 hours later, no hazy water, iron tests at .25ppm. 48 hours later, the same. 72 hours later, the SAME!

So last night, at the 72 hour mark, I plugged my UVS back in. And, a few hours later, HAZY WATER! I tested the iron at 6 hours - .1ppm. At 12 hours - .05ppm. At 24 hours - No iron, GONE!

I had planned on taking a photo of all the tests I had run, showing the mark when I turned on the UVS, but in my excitement of having solved this mystery, I accidently kicked the test tube rack across the living room floor as I lept to my feet. So, you'll have to take my word for it .

I don't claim these findings perfect. After all, it was done in an aquarium, not a sterile environment. But, these findings are conclusive, at least for my tank. UVS does _something_ to chelated iron to make it turn hazy and stop registering on a Hagen Iron test kit.

I plan to leave my UVS off for a few months, and monitor the growth and health of my plants. I've had a few problems with a few different species, and I hope to see improvement. Regardless, I am convinced my data is good re: the iron _controversy_.

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Future tests I need to do:

See if UVS remove gluconated iron as well (Seachem Iron).

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If you own a UVS and dose iron, _PLEASE_ consider running a similar test, and post your results. I'm at the edge of my seat wondering if my results will be repeated in other/all aquariums.

Ted


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## DarkCobra (Jun 22, 2004)

Great experiment, Unirdna!

Does the Hagen Iron test kit specifically test for chelated iron?


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## unirdna (Jan 22, 2004)

DarkCobra said:


> Great experiment, Unirdna!
> 
> Does the Hagen Iron test kit specifically test for chelated iron?


The Hagen test claims to be able to measure non-chelated (free - toxic) iron as well as chelated iron (depending on whether or not you add a white powder to the sample). I tested for both every time. The test for non-chelated iron always read 0ppm regardless of the UVS being on or off.

This leads me to believe that the UVS was somehow causing the iron to precipitate (since there was no "free" iron in my water), causing the hazy water. What I don't know is how this impacts the plants.

I forgot to add. Each time, when I dosed .25ppm iron, the TDS in my aquarium would raise from 300 to 330. Yet, after running the UVS for 24 hours, the TDS would drop back down to 300. This in contrast with not running the UVS; the TDS stayed at 330ppm for the 72 hours I did not run the UVS. Then, when I plugged the UVS back in, with 24 hours, the TDS was back down to 300. I did not feed my fish for the duration of the experiment to prevent water TDS from being influence by their food.


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## putty (Nov 19, 2003)

I'm expecting Mr. Grigg to pipe up here soon with his words of wisdom on what Iron test kits really test. LOL.


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## unirdna (Jan 22, 2004)

putty said:


> I'm expecting Mr. Grigg to pipe up here soon with his words of wisdom on what Iron test kits really test. LOL.


No doubt, much of this experiment relies on the test kit. But, the test aside, how do you explain the TDS and precipitate?

I was on the other side of the fence just a few months ago. All the arguments re: why a UVS can't affect iron seemed solid. But, this new evidence is very compelling and needs to be addressed. If someone has clear explanation as to why I shouldn't believe the Hagen test kit, as well as the rise and fall of TDS and the hazy water, please offer it. I freely admit I lack the tools to scientifically interpret my findings.


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## Rex Grigg (Dec 10, 2002)

Well at least the test kits are consistent.

TDS goes up because you add iron. Once it precipitates out it's no longer a dissolved solid.


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## unirdna (Jan 22, 2004)

Rex Grigg said:


> Well at least the test kits are consistent.
> 
> TDS goes up because you add iron. Once it precipitates out it's no longer a dissolved solid.


That was my conclusion, as well. Do you have any thoughts as to how/why this happens? This seems to be the case, yet I have no idea what the stoichiometry would look like. What would happen to the iron? Tied up and gone forever? Eventually broken down in the substrate, and available to the roots?

As usual, when I do an "experiement", I get an answer for 1/2 a question, while getting 1/2 dozen new ones.

But, for most, we don't have to know how or why (the iron precipitates out) - just that it apparently DOES. And, what does this mean for folks using UV sterilizers who want to maintain any quantity of chelated iron in their water?


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## wapfish (Oct 14, 2005)

Sorry, coming in late on this and haven't read all the past discussions about UV killing chelated iron, but I am curious. Is the general idea about "killing" that the UV is photolyzing the chelating agent, freeing the iron to precipitate out as a Fe3+ salt? Or is something else being considered?

I also get hazy water after dosing Seachem Fe (Fe+2 gluconate) to levels around .1 ppm and have always assumed it was from the Fe+2 being oxidized to Fe+3 and then precipitating out as some sort of ferric salt (phophate, carbonate, hydroxide). I doubt gluconate is a strong enough chelator to hold on to Fe+3 when it's being lost as a precipitate. This presumbaly doesn't happen with other stronger chelators such as EDTA or DPTA since they keep the iron in solution OK. If they were messed up by UV, however, the expectation would be that iron would be lost from solution as a precipitate within a very short time.


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## unirdna (Jan 22, 2004)

Wapfish, what you have described re: gluconated iron is EXACTLY how I understand it. The post-dosing hazy water is a common phenomenom amoung those who dose Seachem Iron. Many in my local club had experienced this; so a club leader recommended Kent Proplant (which uses chelated EDTA iron). Apparently, EDTA iron has a strong enough bond to resist oxidation....unless smucked with UV radiation?

What you've said about Fe3+ precipitation is outside my very limited understanding of chemistry, but I think I followed you OK. If the bonds are broken, the FE is free to form a solid and precipitates out of solution. So, the question remains, in the absence of UV light, what breaks the EDTA bond, allowing plants to use it. The way I see it, unless that plant itself breaks that bond, it will all simply _slowly_ precipitate out, rather than in a 24 hour blast seen when using a sterilizer.

Thoughts? Knowledge?


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## Betowess (Dec 9, 2004)

This is completely over my head. But isn't the reason Seachem's gluconate iron is "preferred" by some is that it is more readily taken up by the plants than EDTA iron. And if it hazes, well, it clears up shortly. Sorry for the hijack. FWIW I only plug in my UV if I do some major disturbance or fear a GW because of what I had heard about UVs messing with the chelated iron...


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## chiahead (Dec 5, 2005)

what about only running the uv at night when the lights are out? Would this make any difference in wether the iron precipitates out or not I wonder?


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## unirdna (Jan 22, 2004)

Betowess said:


> This is completely over my head. But isn't the reason Seachem's gluconate iron is "preferred" by some is that it is more readily taken up by the plants than EDTA iron. And if it hazes, well, it clears up shortly. Sorry for the hijack. FWIW I only plug in my UV if I do some major disturbance or fear a GW because of what I had heard about UVs messing with the chelated iron...


The chemistry is complicated (I don't fully know it myself), but the concept is fairly simple:

If you see that "haze", it means that the iron has broken its "chelated" bond, and bonded with something else in your water column to form a solid. Once you see this, that iron will no longer be available to the plants. It clears up shortly because it settles out of the water. And upon settling out (clearing up), my iron tests read 0 ppm of chelated iron in the water column.

In other words, that "haze" is wasted iron.

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Ideally, what we want is for the plants to take in the chelated iron, and break that bond themselves. That way, the free iron will be used by the plant. If the bond is broken while the iron is in the water column, the "free" iron bonds to something else, and is precipitated into a solid that will no longer be available to the plants. If "free" iron didn't do this, manufacturers would NOT have to bond it up via EDTA or Gluconation. But, it seems that UV radiation also has the power to break that bond. Which means that all the iron is quickly removed from the water column.

The concept of chelated iron works because it stays bonded (inert) until the plants absorb it and break that bond. But, if your sterilizer breaks the bond before your plants get their chance, it is all wasted.

This idea works out beautifully because plants do not need a ton of iron, but they do need a little bit continuously.

To a certain degree, plants do the same thing with the nitrate we add. They would prefer that the N was in ammonium form, but adding ammonium to our tank causes a whole host of problems. So, we add nitrate instead. Plants have to used a lot of energy to break the nitrate bond and free up that N molecule.


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## unirdna (Jan 22, 2004)

chiahead said:


> what about only running the uv at night when the lights are out? Would this make any difference in wether the iron precipitates out or not I wonder?


It would not. If you read through my experiment, you'll see that iron continued to precipitate out of the water (and my test kit continuously showed lower iron ppm) over a 24 hour period. My lights are off for 14 of those 24 hours.


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## unirdna (Jan 22, 2004)

wapfish said:


> Is the general idea about "killing" that the UV is photolyzing the chelating agent, freeing the iron to precipitate out as a Fe3+ salt? Or is something else being considered?


Upon thinking about this quote a bit more, I'm not sure it is a "salt" that will be formed. Salts are ionic compounds that freely dissociate in water. http://www.students.stir.ac.uk/biology/ionpot/iap.htm A solid is certainly formed, but is it a salt? More likely, a covalently (very very strong) bonded solid, suggesting that the iron would likely not ever be available again.... That is to say, never again while in our aquaria.


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## KevinC (May 24, 2004)

unirdna said:


> Upon thinking about this quote a bit more, I think I should clarify that no "salt" will be formed. Salts are ionic compounds that freely dissociate in water. http://www.students.stir.ac.uk/biology/ionpot/iap.htm A solid is certainly formed, but that solid would not be a salt. More likely, a covalently (very very strong) bonded solid, suggesting that the iron would likely not ever be available again.... That is to say, never again while in our aquaria.


Great experiment and results! 

A salt is an ionic compound - it does not have to be soluble in water. Usually we exclude oxides and hydroxides from the definition as well. Many salts are not very soluble in water. 

I'm curious about your phosphate level. Iron phosphate (Iron +2 and/or Iron +3) is very insoluble, and usually the phosphate level is well above the iron level. Carbonate (from KH) is also a possibility.

Kevin


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## unirdna (Jan 22, 2004)

KevinC said:


> Great experiment and results!
> 
> A salt is an ionic compound - it does not have to be soluble in water. Usually we exclude oxides and hydroxides from the definition as well. Many salts are not very soluble in water.
> 
> ...


Thanks for jumpin in, Kevin. Any/all chemistry knowledge is greatly appreciated! 

My water params during the experiment (I should have included this info on the first post :icon_redf )

KH 5
GH 5
pH 6.6
NO3 15ppm
PO4 0.5ppm
TDS 300-330


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## wapfish (Oct 14, 2005)

unirdna said:


> Wapfish, what you have described re: gluconated iron is EXACTLY how I understand it. The post-dosing hazy water is a common phenomenom amoung those who dose Seachem Iron. Many in my local club had experienced this; so a club leader recommended Kent Proplant (which uses chelated EDTA iron). Apparently, EDTA iron has a strong enough bond to resist oxidation....unless smucked with UV radiation?
> 
> What you've said about Fe3+ precipitation is outside my very limited understanding of chemistry, but I think I followed you OK. If the bonds are broken, the FE is free to form a solid and precipitates out of solution. So, the question remains, in the absence of UV light, what breaks the EDTA bond, allowing plants to use it. The way I see it, unless that plant itself breaks that bond, it will all simply _slowly_ precipitate out, rather than in a 24 hour blast seen when using a sterilizer.


OK, I see where this is at now. Iron is a bit complicated. Caution. Geek alert  .

Everything revolves around the fact that Fe+3 is pretty insoluble in almost all its chemical combinations. Nature is full of iron but most of it is extremely hard to get at because it's in the Fe+3 state and tied up as one precipitate or another (all iron -> Fe+3 because of oxidation by atmospheric oxygen). Rust is the most obvious example. Not to say it can't be gotten at, but it's tough. This is the feature that makes iron in many respects the "key" trace element (manganese is similar but used in smaller amounts by organisms). 

With that background in mind, iron availability always revolves around which molecules can grab and hold onto the iron the tightest. Even a very tight chelator like EDTA always has a certain amount of dissociation associated with the equilibrium constant, so the expectation would be that, as you say, over time it will precipitate out very slowly. How slowly, etc, I have no idea, but I think the stronger chelators hold iron soluble for quite a while. On the other hand, the plant does have to disrupt the chelator in some fashion (externally/internally) to get at the iron. Either that or wait for it to dissociate and then grab it. I don't know how it would happen. The specific strategies plants use to get at iron in nature is an active and important area of research. It's clear that plants do have specialized systems for sensing and acquiring iron, however. I have more specific familiarity with bacterial systems, and there it's been well characterized that bacteria make and excrete specific molecules with extremely high iron affinities for just this purpose (siderophores) and also make and utilize specific uptake systems designed to work with these specialized molecules. 

You're basically correct in all you've said except for the part about EDTA having a strong enough bond to resist oxidation. It's really not about oxidation. I'm pretty sure Kent and most chelated iron sources already have iron in the Fe+3 (oxidized) state, and any disruption of the chelator by UV (if this is happening, as your expt suggests) would be some sort of photolysis. Seachem Fe is rather the exception among aquatic iron sources with the iron being in the Fe+2 state and bound to a weak chelator = gluconate. Seachem touts this as making the iron more available to plants since 1) Fe+2 is supposedly more immediately beneficial (doubtful, as the interior of cells is a strongly reducing environment and once inside, Fe+3 would become Fe+2 anyway) and 2) the chelation is weaker so the plant can grab it better. IMO this is just speculative hype, but what works, works, so YMMV.

The way I look at it is that most all iron put in the tank is going to end up as a precipitate, only the timing will vary. Strongly chelated iron will last longer and might be better for plants that are absorbing nutrients primarily from the water column. Iron precipitates in the substrate will be gotten at by plant roots in their own way. Personally, I dose Seachem iron daily at very low dose .01-.02 ppm, so over the course of a week it adds up to around .1ppm total per the general recommendation. I have no idea if this is in any way better than a large dollop at .1ppm once a week. At least I don't see any precipitate that way :smile: . Experience in terms of how well the plants are behaving is the most important thing.


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## wapfish (Oct 14, 2005)

unirdna said:


> Upon thinking about this quote a bit more, I'm not sure it is a "salt" that will be formed. Salts are ionic compounds that freely dissociate in water. http://www.students.stir.ac.uk/biology/ionpot/iap.htm A solid is certainly formed, but is it a salt? More likely, a covalently (very very strong) bonded solid, suggesting that the iron would likely not ever be available again.... That is to say, never again while in our aquaria.


Sorry, didn't see this at first.

It's all a function of the dissociation constant. Some salts are for all intents and purposes insoluble because the two ionic species have such high affinity for each other that water can't get them apart.


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## wapfish (Oct 14, 2005)

KevinC said:


> I'm curious about your phosphate level. Iron phosphate (Iron +2 and/or Iron +3) is very insoluble, and usually the phosphate level is well above the iron level. Carbonate (from KH) is also a possibility.


Righto. I don't dose phosphate and iron at the same time in consideration of just this possibility. OTOH, my suspicion is that it doesn't matter much as the carbonate in our hard water probably overwhelms the iron and knocks it out of solution anyway. One would have to take a close look at the dissociation constants for the various forms.


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## plantbrain (Dec 15, 2003)

unirdna said:


> Thoughts? Knowledge?



Alkalinity plays a huge role in trace metal speciation and presistence.
Harder waters will preciptate more as the pH/alk are higher.

Acid waters tend to complex Fe.

Try another solution/chelators/organic complex, say TMG this time with the UV.

The other thing you can try is using soft RO water.
You will find less preciptate.

Still, as mentioned, the plants gennerally do not need much Fe, but a test kit will measure something that is not bioavilable, so correlating Fe from a test kit and equating it to plant health/growth is a not something you will find to be wise.

The rate of change/removal in the water column as well as mixing plays a huge role there, as does the alkalinity.

FYI, Ferrous sulfate(which disassociates into Fe2+) is added to lakes to remove PO4. Ca preciptates well with PO4 also. See "Apitate".

I've never found any correlation between plant health and Fe levels in the tank(but have with frequency/volume dosing), clearly though, white preciptate is not desirable.
Try a different chelator(DTPH). It'll likely preciptate as well.

Why do you use a UV 24/7 though?
You only need it for green water or the first 24 hours after a large water change.


Regards, 
Tom Barr


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## unirdna (Jan 22, 2004)

plantbrain said:


> Why do you use a UV 24/7 though?
> You only need it for green water or the first 24 hours after a large water change.


Thanks for your insight, Tom. Here's a excerpt from my first post explaining my UV history (and future?). I'm currently NOT powering the sterilizer, though I will leave it inline.



unirdna said:


> I have been running a UVS on my tank since 2 months after it was set up. I bought it to fight off the greenwater my tank had taken on. It did a wonderful job; so I just let it run as a preventive measure against GW and fish disease.
> 
> 
> ....I'm starting to have 2nd thoughts.


Do you know HOW (or if) chelated iron ultimately finds its way into plant tissues. Do plants actively break the bond, and absorb the free iron? Or does chelated iron slowly break down within the water column, and the plants are simply "lucky" to absorb it (before other processes precipitate it)?

If plants need iron (albeit a small quantity compared with NPK), and free iron readily precipitates, then how do plants go about getting their iron. Is it only taken up through the roots (and if so how/why)? Do you contend that liquid iron supplemention isn't useful.

I'm like a 4-year-old with all my questions :redface: .


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## plantbrain (Dec 15, 2003)

unirdna said:


> Do you know HOW (or if) chelated iron ultimately finds its way into plant tissues. Do plants actively break the bond, and absorb the free iron? Or does chelated iron slowly break down within the water column, and the plants are simply "lucky" to absorb it (before other processes precipitate it)?
> 
> If plants need iron (albeit a small quantity compared with NPK), and free iron readily precipitates, then how do plants go about getting their iron. Is it only taken up through the roots (and if so how/why)? Do you contend that liquid iron supplemention isn't useful.
> 
> I'm like a 4-year-old with all my questions :redface: .


The Fe is preciptated, there is no atmospheric component.
So it either stays as a collidal suspension and gets removed by water changes, or it preciptates and falls into the gravel.

Once in the substrate, it can do onen or two things, be reduced back into Fe2+, by either redox conditions by bacterial mediation, or by plant proton pumping that sends out H+'s to reduce the Fe for uptake.

Plants will actively remove the Fe from a chelator or an organic complex like gluconate.

A plant needs a little bit more energy to rip the ETDA out vs gluconate. DTPH is something in between(TMG for example). The plants removes the Fe but leaves the chelator(Kent, TMGS etc) or organic complex(SeaChem) outside the plant cell in the water column.

So the plant actively takes what it needs and the root zone can provide Fe also if the growth rate is slow enough, the roots can provide all the Fe for rooted macrophytes.

ETDA is better for hard water, TMG is good for mid ranges, SeaChem flourish for softer waters.

ETDA does well at higher pH's, such are marine and hard water tanks
TMG does well at a pH of about 7.5
Gluconate does well below a pH of 7.

But that's not to say plants cannot use any of these or you will see a difference due to exclusively this factor of complex/chelator types.

Traces often have other metals in there that play a vital although often ignored role.

These are often chelated with EDTA, so other things play a role also and some traces have more Zn, Mn, B, Cu than others.

Some traces add tannins and other organic acids to maintain them in soluble forms.

An old PMDD trick includes adding a little HCL acid to the bottle to prevent preciptation and mold.

The trade off is when you have low pH's reduction etc, you have less nitrogen cycling and much less bacteria.
Some nutrients are more available, but some are not, like anions, PO4, SO4 etc.

So the trade off is a nice middle ground to get the best for each and using a product that works well in most conditions.

TMG suits that very well.

You can add the Flourish Fe alone as a spike 1-2x a week for fun if you wish.

I prefer the sheen I get on broad leaf plants with TMG.

Trace comparisons are subtle and take time to gauge differences.
It took a long time and lots of comparisons with SFBAAPs folks (back a long time ago now I guess) to get the 5mls 3x a week rule for 20 gal tank with good CO2, good light. 

Most added about 4-8x less traces. I told them to add more, but of course they did not listen because *everyone "knew"* that excess traces caused algae, well, except for me. Finally Claus came to SF (1998?) and told them all their tanks where trace deficient, they added more and a coupe of weeks later they saw marked improvements and no algae.

1ppm or higher Fe was often a level read in my tanks.

The other thing you might consider:
Use the UV in conjunction with the lighting timer, dose Fe at night.

Folks have a long history of leaving their UV's on all the time and dosing Fe and not seeing any differences.

I'd suggested to some at one point that the Fe released is beneficial to plants from the UV.

But as the Fe2+ is released, it is rapidly oxidized into rust/FePO4 etc at common tank pH's.

So that is unlikely.

Regards, 
Tom Barr


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## Betowess (Dec 9, 2004)

plantbrain
Trace comparisons are subtle and take time to gauge differences.
It took a long time and lots of comparisons with SFBAAPs folks (back a long time ago now I guess) to get the 5mls 3x a week rule for 20 gal tank with good CO2 said:


> everyone "knew"[/B] that excess traces caused algae, well, except for me. Finally Claus came to SF (1998?) and told them all their tanks where trace deficient, they added more and a coupe of weeks later they saw marked improvements and no algae.
> 
> 1ppm or higher Fe was often a level read in my tanks.
> 
> ...



Tom, is there a benchmark re: Iron. I find it difficult to get a handle on how much Seachem Iron to add to my soft water. For now I use: "the yellow plant looks like it needs more iron" eyeball method. But I think I have been adding too much which can help BBA, I believe. Thanks, bob


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## unirdna (Jan 22, 2004)

plantbrain said:


> Still, as mentioned, the plants gennerally do not need much Fe, but a test kit will measure something that is not bioavilable, so correlating Fe from a test kit and equating it to plant health/growth is a not something you will find to be wise.





plantbrain said:


> Plants will actively remove the Fe from a chelator or an organic complex like gluconate.
> 
> A plant needs a little bit more energy to rip the ETDA out vs gluconate. DTPH is something in between(TMG for example). The plants removes the Fe but leaves the chelator(Kent, TMGS etc) or organic complex(SeaChem) outside the plant cell in the water column.



Tom, Thanks for taking the time to address my points of confusion. Although I lack the mental tools to follow you point for point, I understood the big picture.

If you'll tolerate just one more [point of confusion]; could you clarify the above two quotes. They seem to contradict each other. If plants can take up chelated iron and use it, how is it not bioavaiable? Is this a "jargon thing" flying over my head?

Thanks,
Ted


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## jimmydrsv (Apr 8, 2005)

I hope no one minds me throwing in my own question but I have been wondering about flourish excel since I first saw this thread. I am wondering how effective the stuff is at reducing iron and making it bio available. Is it something that will improve conditions or will it just reduce a certain amount of iron and limited by the dosage?


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## Betowess (Dec 9, 2004)

dbl.post.:icon_redf


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## Betowess (Dec 9, 2004)

jimmydrsv said:


> I hope no one minds me throwing in my own question but I have been wondering about flourish excel since I first saw this thread. I am wondering how effective the stuff is at reducing iron and making it bio available. Is it something that will improve conditions or will it just reduce a certain amount of iron and limited by the dosage?


I believe excel is an altenative organic carbon source, but not a gas like CO2. It can work by itself, or with CO2 to facilitate photosythesis. Also it will not alter pH like CO2 which will deplete Kh and lower the pH. Most who use it have smaller tanks as its kind of spendy for larger tanks. There has been alot of talk of using it coupled with CO2 as an algaecide as well. I don't think it reduces iron. I think it can be considered as an alternative to gaseous CO2 to promote plant health, but as I said before, usually on smaller tanks because of the cost. HTH bob


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## DarkCobra (Jun 22, 2004)

Gluteraldehyde (Excel) is known to slowly break down into water and CO2. Whether plants are able to utilize it as a source of carbon in a more direct fashion is unknown.

Also, Seachem specifically makes the claim that Excel helps to keep iron in a reduced state. However, as far as I know, they don't explain or give any support for that claim.


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## plantbrain (Dec 15, 2003)

Betowess said:


> Tom, is there a benchmark re: Iron. I find it difficult to get a handle on how much Seachem Iron to add to my soft water. For now I use: "the yellow plant looks like it needs more iron" eyeball method. But I think I have been adding too much which can help BBA, I believe. Thanks, bob


And you would be wrong about believing added iron causes BBA or any algae for that matter. Same deal for PO4, NO3, you name the nutrient(outside variation of CO2 or NH4).

Eyeballing the plant is a good way, as long as the yeyballing is truly isolated from other deficiencies and issues(most often CO2, which is why you have BBA related issues).

By providing good non limiting ranges of everything else but Fe, you can get a good idea of what the tank will look like when it's low on Fe, you raise it up till you no long see any improvements from adding progressively more.

Regards, 
Tom Barr

www.BarrReport.com


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## plantbrain (Dec 15, 2003)

unirdna said:


> Tom, Thanks for taking the time to address my points of confusion. Although I lack the mental tools to follow you point for point, I understood the big picture.
> 
> If you'll tolerate just one more [point of confusion]; could you clarify the above two quotes. They seem to contradict each other. If plants can take up chelated iron and use it, how is it not bioavaiable? Is this a "jargon thing" flying over my head?
> 
> ...


Hi Ted,

Originally Posted by plantbrain
Still, as mentioned, the plants gennerally do not need much Fe, but a test kit will measure something that is not bioavilable, so correlating Fe from a test kit and equating it to plant health/growth is a not something you will find to be wise. 




Quote:
Originally Posted by plantbrain
Plants will actively remove the Fe from a chelator or an organic complex like gluconate.

A plant needs a little bit more energy to rip the ETDA out vs gluconate. DTPH is something in between(TMG for example). The plants removes the Fe but leaves the chelator(Kent, TMGS etc) or organic complex(SeaChem) outside the plant cell in the water column. 



1. So plants remove the chelator(Say TMG) or complex(Flourish), take the Fe2+ internally for assimilation.
2. Different complexes/chelators have better optima for pH/alkalinity for trace metals. While the flourish may require less energy to dislodge the Fe2+ from the gluconate complex vs say DTPH, the trade off is that the Flourish is so weak it preciptates very easily in harder waters(Kh and pH higher).

So while is more available(remember , it is just trace, plants do not need much), over time it is less available than something with a stronger chelator like DTPH, ETDA etc.

So for the plant, you can have a little harder to get Fe2+ all the time, or a easy one for only an hour or two.

Since Fe is a trace, it very tough to gauge what the plant needs in terms of ppm residuals in the water column since you can contaminate things from food, substrate sources etc were this is much easier with something like NO3 and CO2, since they are the lion's share of plant biomass.

So rather than approach this with a test measurement like with CO2/NO3, they have their own issues, we use the plant itself as a gauge, or a bioindicator, phytometer, test kit.

This works much better and tells you what you need to knwo rather than trying to correlate a moving target like Fe residuals in the water column to a good level for plants.

You can do this method for any nutrient also by isolating it by providing non limiting levels of everything else but the nutrient in question and rasie and lower the dependent variable(Fe2+ in this case).

It takes a longer time for a plant to respond to a trace than say NO3/CO2.

So you should give the tank 3 weeks or so before changing a dosing routine for traces.

Roger Miller and myself discussed the issues with testing for Fe in the water column on the APD some years ago. You might want to look there for more info.


Regards, 
Tom Barr


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## wapfish (Oct 14, 2005)

plantbrain said:


> And you would be wrong about believing added iron causes BBA or any algae for that matter.


Hi Tom,

Guess this is my opportunity to try and pick your (plant)brain  about a question invoving iron and algae that's been bugging me. It's not directly related to the original topic of the thread, but sort of close so I hope it's OK. 

Diana Walstad, whom I know you respect but often (?) disagree with, has several pages in her "Ecology of the Planted Aquarium" devoted to iron => promoting algae. She describes the situation where Fe+3 in the water column complexes with DOC = dissolved organic carbon and becomes sensitive to photolysis by light, with the iron being reduced back to Fe+2. In some unspecified way, the algae benefit (preferentially) from this, so she advocates keeping iron in the substrate. From your comment above and from others you've made, it's pretty clear you don't think there's much of a link (if any at all) between iron and algae in the planted tank, so I imagine you don't agree with this.

However, what I was wondering about was whether there might be SOME situations where her idea might be correct. This is based on my own experience with the soft, bright-green beard algae that can grow very long, tends to accumulate up where the light is brightest and, once you have it, seems to benefit from iron additions to the water column. This algae was also worst on my sword and ludwigia, both plants that are supposed to "like" iron. Other people have also posted about this type of algae supposedly liking iron and light.

In my case, I was using Flourish, and the interesting thing is that if you look at the components of Flourish, you'll note the very last ingredient is "protein hydrolysates". Amino acids, peptides (protein hydrolysates) and such are good chelators, so it's obvious that that's why Seachem uses it, but this makes Flourish specifically fit Walstad's idea of iron in the presence of DOC. What I was thinking was that maybe Walstad's idea might make sense in SOME tanks for this kind of algae, if those tanks have more DOC = pollution = bioload to begin with than others. With good husbandry and a well running tank, DOC should be low and there might never be an iron/algae problem. A slightly polluted tank, or one where for example, some wood was slowly rotting or leaching (eg Scolley's Kahuna tank with the giant cypress stump!) OTOH, could be substantially more sensitive to iron as an algae promoter. (BTW, I stopped using Flourish, kept iron in the substrate as she recommends, and the algae went away. I did other things too, though, so I can't conclude anything specific.)

So, after this very long-winded introduction, I'm just wondering what you think about the idea that iron might be more of a problem with regard to algae for a tank that is running less "clean" than another tank with better overall water quality?


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## cyberia (Sep 14, 2005)

UVC & Ozonation DOES destroy chelated iron:

http://www.priva.ca/newsletter/news-disinfectionofrecirculationwater.html

Hope the info helps.


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## unirdna (Jan 22, 2004)

"Destruction of iron chelates is greatest with high-pressure lamps. After a dose of 24 to 28 MJ/cm2 a 33 to 55% reduction in Fe-DTPA was observed. As the dose of UV radiation increased, the reduction of Fe-DTPA increased. At a dose of 277 MJ/cm2 the reduction in Fe-DTPA was 92% (Runia, 1992).

When low-pressure lamps were tested, the rate of Fe-DTPA destruction was greatly reduced. At a dose of 250 MJ/cm2, only 20 to 40% of the Fe-DTPA was destroyed (Runia, 1993)."
*
Thanks for that info, cyberia! I'm going to put in a request for the Runia, 1992/1993 papers.*


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## fresh_lynny (Mar 9, 2006)

unirdna. Thank you for the data on your experiment. It makes sense, chemically. I was asking about a UV sterilizer for quite a while and got mixed responses. Though, microbiologically it made sense to me for fish health, on a strictly chemical level, where the ppt is formed and Fe changes cationic state, I have to say the risk outweighs the benefit until you see a real need to use it, i.e. green water. Then and only then, maybe run it until the situation resolves, then stop again.


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## unirdna (Jan 22, 2004)

fresh_newby said:


> ...until you see a real need to use it, i.e. green water. Then and only then, maybe run it until the situation resolves, then stop again.


My feeling, as well. 

It is easy to become dogmatic when it comes to this hobby. I was a steadfast 24/7 UV guy for 1.5 year.....until I was presented with strong evidence to suggest doing otherwise. I've seen many people completely ignore evidence in order to keep their dogma intact.

Since turning off the UVS on both of my tanks, I have since had to turn one back on a couple times. A handful of my female endlers had some kind of fin disease. Upon running the UVS for a few days, the white discoloration had disappeared (and so had the iron). I lost one female, but the others recovered and no further infections occured. After the dust settled, I simply dosed iron back up once I shut the UVS back off.

The same happened again last week (I think the males stress the females out a bit too much with all the chasing and nipping). I did the same, and got the same results.


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## fresh_lynny (Mar 9, 2006)

unirdna said:


> My feeling, as well.
> 
> It is easy to become dogmatic when it comes to this hobby. I was a steadfast 24/7 UV guy for 1.5 year.....until I was presented with strong evidence to suggest doing otherwise. I've seen many people completely ignore evidence in order to keep their dogma intact.
> 
> ...


Makes sense to me. You have to figure it takes Fe2+ out of solution. The same thing happens in your house with an ozonator, hence the dust falling out of the air. Though it is not exactly the same, on a macro level it mimcs what is happening on a chemical level in your tank.


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