# Ferrous Sulfate?



## OverStocked (May 26, 2007)

The lack of chelators means that the iron precipitates out quicker, which makes it harder for plants to use. Beyond that I do not know how usable it is, as it requires biological breakdown. Someone might have a better answer. 

1 lb of DTPA or EDTA iron lasts longer than most people stay in this hobby...


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## Sharkfood (May 2, 2010)

Thanks for the info. If it requires microbial breakdown, then it would seem to be a poor choice for anything other than use on soil grown plants.

EDTA and DPTA iron are more difficult to find, which is why I was looking at ferrous sulphate. Obviously, cheapness was a major draw also. I thought it would be easy to breakdown based on the ionic bond of the Fe molecule. I also figured it may not be very stable in the solution.

I also thought that the Fe2+ cation might require acidic conditions to be useable.


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## Brian3 (Jan 14, 2008)

I also have this question but no one answer me, How long it need to precipitate. Anyway if it need bacterial breakdown it is only useful on substrate. Still I think usable for that purpose, when making a home susbtrate.


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## Sharkfood (May 2, 2010)

I guess it would work fine added to MTS or something. Maybe even under a planted, aquatic substrate, but I was going to use it for water dosing, and possibly in hydroponics. I'm guessing it won't work very well in those applications judging by what Over_Stocked posted.


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## Brian3 (Jan 14, 2008)

hydroponics plants have a foam to root, so maybe here the bacteria make it available to the plants. Just a thought


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## Sharkfood (May 2, 2010)

Depends on your hydroponic system. I grow mine in straight hydroton, no rockwool. I don't know whether bacteria in the hydroton would break it down well or not. The top inch or so of my hydroton dries more or less completely between flood cycles, but the rest stays moist.


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## Sharkfood (May 2, 2010)

If anyone else is interested in this:

It's been awhile, and I've done some research.

It looks like the major downfall to using iron sulfate is that it precipitates from solution more quickly than other chelates. This supposedly happens very fast at pH over 7. Supposedly this isn't as pronounced below pH 6.5. 

According to one source, magnets in our water pumps cause precipitation to accelerate. It's possible I suppose, but likely over exaggerated in the article. I would think bigger pump = bigger magnet = bigger effect, if there's any effect at all. If this really happens, I would think you'd see iron build up on the magnet over time, and likely would occur with other chelates as well. Impeller drive magnetic fields aren't fixed, and probably just throw the molecule around slightly as it passes by. I'm always skeptical about non scientific articles claiming anything that deals with magnets.

I found links to several aquatic and hydroponic recipes using iron sulfate. I found several that suggest iron citrate also, however I can't seem to locate a source for that compound.

I can't find any literature indicating that microbial action is needed to make iron sulfate bioavailable. It appears just the opposite, that ferrous sulfate gives up it's iron too easily. Strangely, it's supposed to last much longer in soil than other forms.

Oddly, I found one article claiming that EDTA is toxic to plants, although I find that hard to believe.

Some older literature mention ferrous ammonium sulfate, but that wouldn't be my first choice for an aquarium due to the ammonium present. I can't find a whole lot of reference to this chemical in aquatic use, but is sometimes mentioned in terrestial agriculture.

I've found references to iron oxide also (rust). I'm not sure if this would be very bioavailable. It seems like it would be too stable.

In any case, EDTA iron is about $10/lb +, and I can't find it in less than 5lbs. volume. Iron sulfate is 10% of the cost, so I feel an experiment coming. I need to spend some time deciding how I would quantify results. A badly thought out experiment yields junk data.


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## OverStocked (May 26, 2007)

Worth testing, I'm interested as well. I have an iron supplement I thought about selling that is really just a mix of edta, dtpa, and gluconate. Anyone can make it at home, for the price of the salts. 

1 lb of edta lasts a long friggin time, though.


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## Sharkfood (May 2, 2010)

> 1 lb of edta lasts a long friggin time, though


Lol. That's why I don't really want to buy 5#.


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## Brian3 (Jan 14, 2008)

for the price of the ferrous sulfate, give it a try. I think that the best way is to use micros without iron, for iron ferrous sulfate, that would be interesting.


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## noxious_nasties (Nov 30, 2012)

Sorry to dig up an old thread, but as it came up on a google search on the topic - anyone wondering the chemical answer to this, the stuff is useless for planted aquariums as it virtually precipitates immediately. Iron sulphate is unstable in the 2+ form (ferrous) and thus quickly 'reduces' and loses an electron to become more positive - the 3+ (ferric) state. A chemistry friend of mine and I concluded that the oxygen in the tank water is likely to be the main cause of accelerating the precipitation. Anyone dosing the tank will see an immediate white cloud form - it is therefore precipitating immediately, rendering it useless for plant growth. The 2+ form is the state plants require for easy uptake, not the 3+. You will not find it in any commercial fertilisers for this reason. Chelation stops this process (for some time), giving the plants more time to absorb it. I've tested it personally and came to this conclusion through both real life observation and a reasonable understanding of the chemistry. 

Cheers,
John


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