Teach me about iron …

[*Ci*]

I have 3 large tanks, med. tech, mostly undemanding plants. For micros I have been dosing CSM+B, which I’m pretty sure has some form of iron, and because I have some vague notion that it might not be the right kind, I also dose Seachem Iron. These micros and iron are dosed daily. I’m getting tired of the expense of the Seachem product, and I need to know, a) if I really need it, and b) what dry iron compound can I mix myself, that is cheaper and available in Canada?

So, can someone please explain, in simple to understand terms, about the different chelates of iron and which kind is needed and when? And then help with my questions?

 

[GreggZ]

To make it simple.

CSM+B uses EDTA as a chelating agent. It is most effective at pH 6.5 and below.

DTPA is most effective at pH 6.5 and above.

And then there is Ferrous Gluconate which is non chelated and only available for a short time.

So which iron will be most available to your plants depends on the pH of your water. Lower pH EDTA, higher pH DTPA. And plants love some Gluconate but more so with higher light fast growing plants.

If you want to stick with CSM+B, and your pH is on the higher side, then you could add some DTPA to your mix which will be MUCH cheaper than any liquid iron supplement.

If you want to dig in deeper into micros here's a link to a post from my journal.

GreggZ Custom Micros

 

[JayP]

To make it simple.

CSM+B uses EDTA as a chelating agent. It is most effective at pH 6.5 and below.

DTPA is most effective at pH 6.5 and above.

And then there is Ferrous Gluconate which is non chelated and only available for a short time.

So which iron will be most available to your plants depends on the pH of your water. Lower pH EDTA, higher pH DTPA. And plants love some Gluconate but more so with higher light fast growing plants.

If you want to stick with CSM+B, and your pH is on the higher side, then you could add some DTPA to your mix which will be MUCH cheaper than any liquid iron supplement.

If you want to dig in deeper into micros here's a link to a post from my journal.

GreggZ Custom Micros

Well, that's much better than my suggestion which was to just throw in a Flintstones vitamin each day.

 

[Unexpected]

GLA sells a mix with both EDTA and DPTA. It's still CSM+B though. And I think, if I recall correctly, Joe telling me it's low on boron. If you are in the USA, I highly recommend grabbing Micros from him. He has several options.

 

[*Ci*]

If you want to stick with CSM+B, and your pH is on the higher side, then you could add some DTPA to your mix which will be MUCH cheaper than any liquid iron supplement.

I do want to stick with CSM+B for now because I have a lot of it and am satisfied with my plant health. What is DPTA, is it a powder I can buy and just add to the micro stock solution.
Sorry for being so ignorant about this - things going on in life that are occupying all my brain cells : )
Th pH in my various tanks are all above 6.5, ranging between 7 and 8.

 

[*Ci*]

GLA sells a mix with both EDTA and DPTA. It's still CSM+B though. And I think, if I recall correctly, Joe telling me it's low on boron. If you are in the USA, I highly recommend grabbing Micros from him. He has several options.

I’m in Canada … nothing is easy to get, everything is expensive to ship : )

 

[Unexpected]

I’m in Canada … nothing is easy to get, everything is expensive to ship : )

Can you get Boron up there? I know @Pepere uses CSMB and then added a few things to boost it up.

 

[ElleDee]

@*Ci*, I found this article to be very helpful: Iron supplementation and management in aquaponic systems: A review.

Your pH affects iron availability, but there are a few other factors to consider. If there is iron in the substrate, rooted plants can modulate the soil environment to make iron available for uptake. Some species are better at doing this than others though - for instance I'm finding that Mayaca fluviatilis is a big baby about iron, rooted or not. (In terrestrial plants you see this often in plants that evolved in acidic soils where iron is present and available, so they don't have any reason to develop all the iron-scavaging techniques. Sometimes people say that these plants are "iron hungry" but that's not what's happening - typically there is enough iron, they just can't use it.) Also, if you are dosing in the water column daily, you can probably get away with an imperfect chelate in a lot of circumstances. If EDTA is easily available, you can always try it an see if you start to see problems? Iron deficiency shows up as white or translucent new growth (very freaky and weird, not subtle) and rectifies quickly when the plants get iron.

Also, DTPA stability tops out at 7.0, so from a pH perspective EDDHA is the best fit for you. You may not need it for the reasons above, but if you are going out of you way for the right chelate, that's the gold standard. I have no idea how available it is in Canada though.

 

[Pepere]

I used to use the Green Leaf Aquatics micromix with EDTA and DTPA. I added extra Zinc (I think the Boron strength in it is fine, the weak compound was Zinc.). and a tiny wee bit of nickle.

I have since switched to mixing my micros all from compounds following the recipe @GreggZ listed on the forum.. I have better than half a tub of the GLA micromix still kicking around. The micromix powders no doubt contain all the compounds in the right ratio if you mix an entire tub at once.. my concern is that the various compounds are of varying density, and I did not have confidence that individual batches had the correct ratio of each compound in them.

As each batch has each compound weighed out now, I have confidence each batch is consistent.

I spent roughly $140.00 for all of the compounds and most of them I have a few lifetimes of supply of. The only compounds I forsee having to buy again with any regularity would be the Iron powders and maybe the boron and zinc. The iron powders I have at least a 3-4 year supply of from my initial purchase

 

[*Ci*]

Ok, so I see that Seachem Iron is ferrous glucanate, and from what @GreggZ said, it doesn’t last long and maybe I’ve been wasting my money on it anyway. I can get Iron chelate DTPA 11% here, I just need to figure out out how much to add to my mix … I’ll use rotalabutterfy.

 

[Naturescapes_Rocco]

Fe Gluconate is probably best used with every-other-day dosing, or every-day dosing, since it doesn't last long. Once weekly or even twice weekly dosing probably is better with DTPA, which is what I use.

 

[BenB]

DTPA is most effective at pH 6.5 and above.

Ugh... I knew these were affected by pH, but I had my ranges messed up. My tank hovers around there to lower. What if I use.....

Fe Gluconate is probably best used with every-other-day dosing, or every-day dosing, since it doesn't last long. Once weekly or even twice weekly dosing probably is better with DTPA, which is what I use.

.... never mind. Rocco answered it. I expected I was OK with just gluconate if I dosed daily, and I was wondering what the half life was. It seems I am.

 

[GreggZ]

Ok, so I see that Seachem Iron is ferrous glucanate, and from what @GreggZ said, it doesn’t last long and maybe I’ve been wasting my money on it anyway. I can get Iron chelate DTPA 11% here, I just need to figure out out how much to add to my mix … I’ll use rotalabutterfy.

If you need help let me know. Once you do it once you will realize it's really very easy to calculate.

 

[JacksonL]

@*Ci*, I found this article to be very helpful: Iron supplementation and management in aquaponic systems: A review.

Your pH affects iron availability, but there are a few other factors to consider. If there is iron in the substrate, rooted plants can modulate the soil environment to make iron available for uptake. Some species are better at doing this than others though - for instance I'm finding that Mayaca fluviatilis is a big baby about iron, rooted or not. (In terrestrial plants you see this often in plants that evolved in acidic soils where iron is present and available, so they don't have any reason to develop all the iron-scavaging techniques. Sometimes people say that these plants are "iron hungry" but that's not what's happening - typically there is enough iron, they just can't use it.) Also, if you are dosing in the water column daily, you can probably get away with an imperfect chelate in a lot of circumstances. If EDTA is easily available, you can always try it an see if you start to see problems? Iron deficiency shows up as white or translucent new growth (very freaky and weird, not subtle) and rectifies quickly when the plants get iron.

Also, DTPA stability tops out at 7.0, so from a pH perspective EDDHA is the best fit for you. You may not need it for the reasons above, but if you are going out of you way for the right chelate, that's the gold standard. I have no idea how available it is in Canada though.

Really informative post!