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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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Yes, tobacco is an old-timey pesticide that I love.

Highly effective, inexpensive, and completely organic.

And it doesn't burn the gardener, as hot pepper sprays tend to do.

When I had a truck garden I used to raise a few tobacco plants just for that purpose.


TC and Chip,

I've searched and searched,

but can not find an answer to this question:

how much Maxicrop or equivalent

('Marinis' here in western Canada)

would you use in a well-planted brand-new system?

Jon...Ever since that conversation over in the Fish-less group (shameless plug) I too have been giving the iron cycle (and how to use it to an AP operators advantage) an un-healthy amount of thought. Various anoxic Ruth Goldberg type contraptions have materialized and dissapated in my head...Unfortunately (or not) the US Steel plant here where I work(ed) as an engineering consultant was just sold for $1.00 USD...yep a dollar...So the AP greenhouse and this whole farm is starting to take on new, weird business-y dimensions to the otherwise fun-hobby personal research vibe. So in 'the new reality' EDDHA it is...

That being said though...whatever and however you decide to do this, keep in mind that as soon as your freshly bacterially chelated iron water is re-oxygenated or enters a fairly oxygenated environment, different bacteria will start to convert it back to ferric iron, but like Nate said (luckily in this case) its a 'slow' process. Just keep that in mind though when running numbers/sizing.

I like the idea of a completely separate device that is unconnected to the AP system that you could convert and keep  iron rich water anoxic until you need it. Then maybe introduce it in a batched rush directly after the fish tank (i.e into the media beds or raft) and let it do its thing. This could be done on a given 'regular' basis rather than a constant trickle through type set-up. (Take all this with a grain of salt as they are just opinions of mine based on how I've perceived things). There are a couple reasons I think this though, which may or may not be misguided. One being that it may work too well. I know that it is different for each species, and your Talapia have probably survived a lot of different things you've thrown at them...but the iron could tax their gills. Iron in as much as I'm aware of, in fish, wont accumulate in their plasma  or even gill tissue, the mechanism of iron toxicity in fish appears to be physiological accumulation on the gills themselves, causing clogging and gill damage. Not inside of any tissue or blood. (Acording to a study done by D. J. B. Dalzell and N. A. A. Macfarlane. On Brown Trout. Published in the Journal of Fish Biology Vol.55 Issue 2 pages 301-315

If I remember correctly, the geometry of a hydrocyclone is really complex, (well that's how it was treated in an industrial setting anyways, it might not need be in a home variation though). The density of what you are separating (fish poo in this case) will (should) determine in large part that geometry. There are lots of different ways to make a swirl filter as I'm sure you're already well aware of :) The hardest part about it seems like getting the math right for the cone at the bottom for a given diameter barrel, if your fabricating it yourself out of something flat.

I think I can dig something up on the hardrive for if you want to build your own. The design should be relevant to fish poo applications. (This is before I decided to put in 8 media grow beds that are now in the GH to act as solids filtration for the 546 sq.feet of DWC rafts I will continue building when the weather permits). It maybe needlessly complicated and/or too much detail and data...But you might dig it nonetheless...sorry for rambling....

Jon Parr said:

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.

Old timers here used to save their hand rolled buts for the same reasons. Had no idea it would work on mites and aphids though. Very very cool. (unless its the just all the pesticides that they sprayed the tobacco with working hehe...kidding)

Chip Pilkington said:

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... 


     I think once upon a time I figured out the aprox square footage of my plant beds and then figured out what the seaweed extract bottle recommended.  Like if it says use one cap full in a gallon of water to use on 100 square feet.  Instead of adding the cap full to a gallon of water and watering the plants, I just added that cap full to the grow bed.

That above example was just numbers pulled out for the example.  Read the bottle and do your figuring.

And I usually use like an ounce per grow bed in my systems, my grow beds are mostly 100 gallon beds.

Thanks, TC.

An ounce per 100-gallon bed?


That's an amazingly small amount.

I appreciate the guideline of the surface-area recommendation.


I admit that my methods have been largely unscientific but an ounce or two in each grow bed is still able to tint the water in the whole system a darker color.

Vlad, I'd love to see your plans.  The opinion of the pro I've been talking to is that the fish solids are not heavy enough to be removed by hydrocyclone. But a swirl filter would accomplish the same task.  Instead of flushing the solids and removing from the system, one could add them to the biodigester, and the effuent could be returned to the AP system.

Now I'm no pro and I could be wrong but...I think that you could use a hydrocyclone for fish poo if you respect the geometry and velocity that the fish poo would necessitate IMO. Are these pros using one to separate rock dust heavies? He is probably right, in that, that particular shape/model hydrocyclone probably wouldn't work. Your fluid resistance to centripetal force ratio would probably need to be lower for fish poo than for granite dust I'm guessing.

Here is a Funner than Chewing on Broken Glass While Falling Down Seven Flights of Stairs, Numerical Analysis of a Hydrocyclone in RAS,  brought to us by the South Korean School of Mechanical Engineering Pukyong National University...complete with exiting graphs, charts and mathematical models!!!

Still, a swirl filter to bio-digester would pretty much do the same thing.

And on that note here's another oldie but goodie...


Dang, Vlad.  Given the choices, I'll opt for the broken glass and stairs.  That is "skill level II"

I'm familiar with the youtube clip, although i think the cone placed in the bottom with duct tape would have sufficed, and water would have provided the back pressure.  The concrete and thinset seems overkill, but nice I suppose.  

I compiled the results of the following study - Nutrient Cycle and Sludge Production During Different Stages of Red Tilapia Growth in a Recirculating Aquaculture System (Gholamreza Rafiee & Che Roos Saad)


The table below shows the percentage of feed nutrients that were found in the water column (dissolved nutrients), fish flesh, and sludge at different Tilapia growth stages. The pH during the study ranged between 5.89–6.77. What's interesting to note is the high percentage of some nutrients that settled out even though the pH was relatively low. 

WATER Average
Fish Weight (gm) 20 40 80 120 180 88
Fe (%) 6.4 6.4 6.4 6.4 6.4 6.4
Mn (%) 6.4 6.4 6.4 6.4 6.4 6.4
Zn (%) 6.4 6.4 6.4 6.4 6.4 6.4
Cu (%) 6.4 6.4 6.4 6.4 6.4 6.4
Ca (%) 6.23 5.31 5.21 4.1 6.03 5.38
Mg (%) 80.9 57.86 23.09 51.94 49.41 52.64
N (%) 10.19 7.28 2.9 6.54 6.22 6.63
P (%) 28.04 33.13 30.94 18.93 27.88 27.78
K (%) 38.17 38.04 26.55 23.68 35.07 32.3
FISH Average
Fish Weight (gm) 20 40 80 120 180 88
Fe (%) 10.01 6.3 6.18 11.55 0.02 6.81
Mn (%) 5.34 6.04 5.57 5.79 0.02 4.55
Zn (%) 0.75 8.33 9.83 38.38 0.02 11.46
Cu (%) 27.21 30.41 8.1 1.37 0.07 13.43
Ca (%) 34.66 33.65 22.1 33.77 9.86 26.81
Mg (%) 8.85 4.23 5.37 5.98 5.03 5.89
N (%) 27.87 31.22 36.56 34.48 32.53 32.53
P (%) 14.08 19.14 20.36 19.16 7.18 15.98
K (%) 6.85 7 8 8.59 5.38 7.16
SLUDGE Average
Fish Weight (gm) 20 40 80 120 180 88
Fe (%) 92.5 89.17 97.07 93.84 86.05 91.73
Mn (%) 26.96 22.89 17.73 22.14 21.49 22.24
Zn (%) 27.08 20.95 21.43 27.84 23.93 24.25
Cu (%) 73.19 60.08 39.64 61.95 46.17 56.21
Ca (%) 21.14 18.26 16.55 22.05 15.71 18.74
Mg (%) 8.06 8.39 8.07 11 88.87 24.88
N (%) 23.64 15.93 14.94 19.44 17.9 18.37
P (%) 6.91 4.56 4.39 6.59 5.55 5.6
K (%) 4.07 6.83 5.08 7.31 5.85 5.83

Terri, what units are the numbers given?  Maybe parts per million (ppm)?

Remember that you are seeing the results in recirculating aquaculture where they collect and remove the solids from the system and generally don't give them much chance to be mineralized so if they were not being excreted from the fish in liquid form, they were probably in the solids or sludge since they are not adding any iron or metals to their water, most things that were not in the source water got into the system in the fish food and most things not ammonia or CO2 come out of the fish in the solids rather than in the liquid form and will therefore be in the sludge.

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