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Re: Actinic lights and algae problems

>  > While I was talking to
>  > Greg Morin of Seachem on the phone awhile ago, he
>  > mentioned how gluconate bound minerals are either used
>  > rapidly by plants or precipitate.  It would seem to me
>  > then, that unlike iron edta (for example), gluconate
>  > complexed elements are not in the water long enough
>  > for the any actinic light to perform this dirty deed.
>At least according to what I read in Diana's book, this photoreaction can
>break the chemical bonds holding the Iron for either iron + EDTA or iron +
>DOC. I may be wrong, but wouldn't gluconate be classed as a type of DOC?
>As for Greg's assertion that the iron in Flourish and Flourish Iron not
>being in the water long enough for this reaction to take place I can't
>venture anything - I don't know how long this sort of reaction takes to
>occur. From what Diana reports, I gather its pretty quick. But remember also
>that it wasn't too long ago that Greg was assuring us that gulconate
>complexed Iron was in the water column long enough for plants to get at the
>James Purchase

Sorry James, better reread the above quote ;-)

Ryan Mills made that supposition based on my comments... I didn't say 
anything about this reaction taking place or not taking place in my 
conversation with Ryan. What I stated to Ryan is that the iron in 
Flourish and Flourish iron, (which is gluconate bound) is maintained 
in the ferrous +2 state for a relatively short period (several hours 
to a day). Although this is a short time frame, those plants which 
are active foliar feeders are able to rapidly utilize this iron 
because it's already in the form they prefer (ferrous). After that 
time frame the unused material will be eventually be oxidized to the 
ferric (+3) state at which point it will quickly precipitate with any 
of a variety of anions in the water... settles out in the substrate 
where the roots can utilize it in the same manner as they can any 
iron source in the root zone. So in the end, nothing goes to waste.

So, now my comment on the photo reduction of iron: Since the iron in 
Flourish and Flourish Iron is already in the reduced +2 state, there 
is nothing to reduce, so this shouldn't be a issue. Reduction of the 
gluconate itself (if this even occurs under these conditions) would 
not substantially change the mode of binding, so this would not 
result in the release of free ferrous iron.

Based on Roger Miller's comments to your original post it appears to 
me that the main concern here with this reaction is that EDTA bound 
ferric iron will be reduced to release free ferrous iron (in the 
presence of strong actinic lighting), thus yielding a source of iron 
very readily used by algae.

Since we are still selling quite a lot of Flourish and Flourish Iron, 
I would have to conclude that people are not having massive algae 
outbreaks using these products ;-). Thus it follows that the algae 
are not able to utilize the gluconate bound iron and the plants are 
(or that the plants are able to use it many orders of magnitude more 
rapidly then algae). So I suppose the solution here is: if you want 
to use actinic lights but are concerned about this issue... use 
Flourish Iron ;-).

-Greg Morin

Gregory Morin, Ph.D.  ~~~~~~~Research Director~~~~~~~~~~~~~~
Seachem Laboratories, Inc.      www.seachem.com     888-SEACHEM