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Chelated Iron Dosing - Is there such a thing as a preventive dosing?

Is there a specific dosing of chelated iron that one can add to his system as a preventive dosing!

I know that when you see yellow leaf appearing it is normally time to add chelated iron. This said, I would like to know if there a specific dose that you can add weekly, monthly to keep your AP system in a happy iron level?

Not too much, not too high... just enough to avoid a lack of iron!

Some specs:

  1. I have a chelated iron EDDHSA 6% (Fe)
  2. Using a IBC tote with 1000 liters water +/-
  3. 2 x (4x8x12inches) Deep Floating Raft 
  4. PH is at 6.8 / 7 range

Any advices would be welcome!

Roger Pilon

Costa Rica

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That sounds like a great promotional point, Chip.

Can you give us a source to quote on that?

Hi Shas,

I thought about that while making the comment, but was too lazy to look it up - let me see if I can find it. No promotion intended, just a little peace of mind with all of the toxins in the environment.

I remember it well, as at the time, I was trying to make my fish selection. Also, living in SE Asia, where water quality is a huge issue, I wondered about the risk of eating Tilapia I'd caught in both Indonesia and Thailand.

During this particular research session, I read about Tilapia being raised in waste treatment facilities in China and Vietnam, as well as other less than ideal conditions. Here in Thailand, they are often raised in irrigation water which has got to contain some of the highest pesticide concentrations in the world...several countries have threatened to ban Thai veggie imports over their unregulated use of chemicals. That said, it practically takes a nuclear device to combat bugs in this country. The farmers are really challenged here. It's also really tough trying to defend an AP system against the little monsters.

I'll look for the source data behind my comments on Tilapia.  

Looks like my memory is fading a bit - I got the "feral" part mixed up as they appear to retain higher levels of mercury. Still looking for the original article. This comes from a Wiki clip, but it's not what I'm looking for:

Tilapia have very low levels of mercury,[15] as they are fast-growing, lean and short-lived, with a primarily vegetarian diet, and so do not accumulate mercury found in prey.[16] Feral tilapia, however, may accumulate substantial quantities of mercury.[17] Tilapia is low in saturated fat, calories, carbohydrates and sodium, and is a good protein source. It also contains the micronutrients phosphorus, niacin, selenium, vitamin B12 and potassium.

What I am finding is that while they do resist mercury to some extent, they appear to be vulnerable to lead, which is not good. There is also much more critical and/or negative data currently available than when I did my initial fact finding several years ago.

I will make sure my data is current and consistent next time - sorry.

Iron toxicity is rare but will show up mostly in young plants on older tissue as bronze or rust colored flecking or spotting along with stunted growth.  By and large though it's not something you need to worry about in most systems.  It's better to go over than under on iron.  Vlad you're right, anoxic reduction can make iron available in system but it's a slow process and may be limiting for most folks who don't want to devote much system space to create anaerobic zones- although you're also correct when you mention that they occur on many (especially pitted or textured) media surfaces. (although even the effectiveness of this is dependent on  The reality though is that with iron hogs, you will have to dose.

When you add bases to your system often you will see precipitate develop- this may be Ca or K precipitating out as a carbonate, but often in Fe rich systems its an iron precipitate- either iron carbonate or iron hydroxide.  It's usually a white, cloudy precipitate at the point where you introduce your base.  this is expecially common if you're dosing with cheap iron sulfate.  It's a nice way to check iron (if you know your K and Ca are balanced) besides waiting for deficiency.

Chip- ferrous sulfate is not as stable as chelated iron in the system.  If your water is highly aerobic you have to watch it- (one reason I am NOT a fan of Maxicrop- even though everyone uses it. . .)  In reality, systems do not need micronutrient supplements if they are feeding their fish.  (Ok, I add epsom salts, dolimitic lime and a pinch of borox every 6-8 mo.s, but it's not always needed).  Switching to chelated iron will make more iron available in your system- especially at higher pH values, where ferrous sulfate fails miserably.  Ferrous sulfate is fine in low pH systems but I wouldn't bother with it over 7. That's when you need a chelate.  If you have a high carbonate system, or supplement with CaOH EDTA won't work anyway- you want EDDHA or DTPA.  That's really the benefit of a chelate- at neutral to high pH iron salts are fairly worthless (i.e. maxicrop), but chelates will remain somewhat plant available.  Unless you run at low pH values, or have lots of anoxic BSA for iron reduction you have to use a chelate.  Although it may be possible to use some grains for natural chelation.  (Many plants synthesize chelatins naturally- oh, and chelated iron is allowed in organic systems.)

Anyway, as far as practical advise- I think you'd get much better results if you did foliar applications- I don't even know if you can do that with maxicrop. . . .  That's how most ferrous sulfate is applied, when not in low pH environments. . . 

Shas Cho said:

"I read recently that iron is unique among the micro nutrients in that you cannot overdose."


Animals (eg, humans) can certainly overdose on iron

and it can be pretty darned nasty:


"Iron overdose has been one of the leading causes of death caused bytoxicological agents in children younger than 6 years."



"Iron products can be very dangerous for children."



Iron overdose seems to be less dramatic in plants:


"Excess Fe can result in Dark green foliage, stunted growth of tops and roots, dark brown to purple leaves on some plants (e.g. bronzing disease of rice)."



And of course excessive iron levels in plants

can cause iron toxicity in the animals which ingest them,

bringing us back to point one.


I am not aware of any substance,

including water and oxygen,

which cannot be harmful in excess.

Overindulgence in even Cannabis and Vitamin C cause SOME side effects!

Thank you Nate. A few minutes of your time saves the rest of us hours of sifting through research and finding what's applicable to AP.

I've been intrigued with the iron cycle lately, and Carey's biodigester. I'm wanting to expand from my media system and include a raft. I do not have a solids filter now, other than the media. I'm a big fan of preplanning and going to great lengths to save me money and maintenance in the long run. So, if my devious mind is thinking right, then I'd like to pump the fish tank solids through a hydrocyclone. The hydrocyclone dribbles the solid out the bottom like wet mud, and returns the clarified water to the FT (or wherever you want it). The fish solids would simply drop in the feed tube of a blue barrel biodigester containing iron. The biodigester would be too small, I think, to produce a worthwhile amount of methane, but would do a fine job of conserving nutrients in the solid waste making them water soluble, and perhaps keep up with the iron demand. You mentioned Biological chelation of iron is a slow process, but if the digester was sized right it should maintain once started, eh?

The methane produced could blow up a baloon, and you could burn it off as needed, adding co2 to the room. I originally started tinkering with the hydrocyclone idea to filter solids to a worm bin, and the leachate could simply drain back to the FT, but I want to get the iron in there somehow. Actually now that I think about it, a worm bin could be constructed with an anoxic sump full of iron, and leachate could be drained off at midlevel. Hmmm.

Anyway, feedback appreciated. I do granite fabrication for a living, and hydrocyclones are used to filter the stone silt out of the recycled lubricating water, without ever changing a filter. I assume fish waste is heavy enough to be separated by spinning. Stone silt is 90% filtered in one pass, and if left on continually will clear the water completely.

Chip Pilkington said:

No promotion intended, just a little peace of mind ...


Good morning, Chip


I was not using 'promotion' in any negative sense.

I was thinking more of encouraging folks to support and engage in AP,

and to purchase AP-grown foods.

My background involves a lot of reseach,

and I am aware of the foibles of human memory.

I have often been surprised and even dismayed

to find, when I go back and look something up,

how much I have forgotten or even re-written in my mind.

So I am always reluctant to pass on information

that is not supported by either a citation or personal observation.

And recent observation at that;

"I remember walking three miles to school,

barefoot in blizzards and up-hill both coming and going."


It's certainly true that lean, short-lived vegetarian fish

are going to accumulate a lot less mercury

than, say, tuna.

This is good information, Nate.

I am very ignorant about chelation;

what happens to the chelates after they deliver the iron to our fish tanks?

The DTPA arrives, bonded to Fe.

Then what?

Why does it not release the Fe and then bond to zinc or other micronutrients

(I'm assuming that most AP water will have calcium to spare)?

Is it a matter of relative concentrations,

or am I on the wrong track altogether?

Hi Shas,

No worries, I understood what you meant and I agree.

Hi Nate,

I've been thinking about how best to reply to your comments about both seaweed products and the ferrous sulphate.

One of the challenges I have faced in this hobby is that my systems (and often other poster's systems as well), do not always follow the laws of chemistry to the letter. There is debate and disagreement on the use of products, chemicals, etc as well as their effects on water and the system overall. There is also some inconsistency in how individual systems respond to treatments and/or develop and mature.

Personally, I don't introduce much into my systems. For example, I prefer to let things like pH settle with the system rather than chase it up and down with chemicals. That said, when you attempt to raise "needy" plants in a new system, practical experience has shown me that seaweed products work and work well. I didn't come up with the solution on my own, rather I was guided by some experienced folks on another forum (wasn't a member here at the time). Like many, I jumped in both feet and started planting. Virtually everything in the system stalled after a few weeks and literally stayed in limbo for two months. I asked for help and was brought up to speed as to what was going on and why the system was behaving as it was. My system was fully cycled but not ready for the tomatoes, cukes, cabbage and all the rest I had planted. Seasol was recommended (I belonged to a few Aussie forums). I ended up using a BioCanna product on one system and then the Maxicrop on another. It was immediate change - the plants shot up, produced flowers and fruit before my eyes. The cabbage blew up (and I learned a bit about managing GB space).

Had it just been one system, I might have considered other factors. Bottom line - two independent system, several months apart, showed the exact same response to the products. No adverse effects to fish or water least not in the categories I am able to test in. I do respect your opinion - you are an incredible source of information, but in the case of the two seaweed products, my personal experience appears to differ from yours. I don't remember if anyone told me to keep it to just lettuce at that I think about it, I had my first system built before I joined a forum or asked any questions. My experience with the products were consistent with the experience of those who had recommended them.

As to the ferrous sulphate, I read up on it when I was first introduced to the maxicrop products as it made up the "plus iron" component. I had been experiencing some deficiencies, and both iron and potassium were recommended on the forum. Trying to source a "chelate" product in Thailand is difficult, even with a translator. When I found the plus iron variation for maxicrop, I thought I'd give it a go. The potassium I dealt with in the recommended Aussie way - banana peels. They are quite abundant here and they may have helped. The canna product actually contains potassium so that helped as well. Anyway, I searched through many forum discussions, as well as the typical Google sources. What I found was that according to some experienced APer's, ferrous suphate was acceptable, but at that point, I only cared that it was safe and a viable alternative already included in the product. The interesting part is that my system was bouncing in the high 7's-8 for pH. My hope was that the ferrous sulphate would bring the pH down a bit. The reality is that it's such a low dosage through the product that it didn't do much either way. Plant conditions on the other hand, improved greatly. Here again, how could the plants respond to the iron with a pH level pushing 8? But they did.

It's challenging for many of us in that we aren't chemists or biologists. I don't know that we need to be. AP is a fun, but rather expensive hobby which happens to kick out some nice fish and veggies from time to time. It's also not rocket science. I've got very healthy systems based on some best practices taught through these forums, but mostly I don't push things. I test, but only react when the system requires it. This thread began and is actually based on treating something that isn't even a problem yet. It's been an interesting thread, but one that conflicts a bit with my strategy.   

The point of this post was actually meant to share the challenges many of us face in the advice we receive, particulalry when some very credible sources are a bit inconsistent or actually disagree. As hobbyist's, we take a leap of faith every time we take action, as we aren't subject matter experts. Of course that doesn't stop many of us (myself included) from sharing what we've found to work best.


Chip, the maxicrop also provides potassium and other trace elements so if you got the same results with the potassium product as you did with the maxicrop plus iron, are you sure it wasn't just the potassium you were lacking?

And I don't think Nate was really Knocking maxicrop in general but just not really endorsing the maxicrop plus iron as a particularly effective source or Iron supplementation if you are experiencing severe pH related iron deficiency.  Maxicrop is a great source of potassium and trace elements but I don't recommend heavy use beyond the first maturation period of the system.  After that first period it should only be used on a more as needed basis rather than regularly.

And Nate, Maxicrop or maxicrop plus iron would be good as a foliar feed.  (Just don't do it mid morning on what will be a hot sunny day as burning could happen and don't mix stronger than recommended.)

Hi TC,

I understood Nate and I mostly agree with him, though he was clear that he's not a fan of maxicrop. Had I started the system more conservatively, I probably wouldn't have needed it. That said, it allowed for a fully developed crop of veggies that had no business being in my system at that early stage.

The iron and potassium deficiency was diagnosed based on symtoms and pictures I submitted. It was also consistent with what I could find online for dirt-based plant ailments. No doubt potassium was the major deficiency.

Once again, I see so many posts from folks with new systems and veggies stalling out. i just want to stress that there is help for them. 

I have also used as a foliar, but as much to discourage bugs as for the nutrients. It will definitely burn plants - I recommend using just before dark, as that's when the critters come (and of course the plants won't be burned). This is a bit off topic but I recently experimented with a tobacco based spray for bugs which was recommended by the local hydro shop - it worked very well. I boiled water and then added a small pack of tobacco (it's a very cheap Thai "roll your own" product) and brewed a tea. The boiling was to kill any tobacco related virus which could infect other plant varieties (Rupert's advice). I used the spray on a number of plants assaulted by worms/caterpillars, aphids and mites. I treated one time and those plants did not require another. I was skeptical, as I didn't want a tobacco tasting salad, but the stuff washed off easily.

Cool, that's interesting about the tobacco.

It worked well with no adverse effects. I would imagine it would be rediculously expensive to use in the States or Australia.

The concept is sound - the smell and taste of tobacco would certainly discourage me... 

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