Photo degradation of FeEDTA with Time in Commercially Produced Soluble Fertilizers ie Master Blend and Peters. by: Joseph P. Albano and William B. Miller
www.researchgate.net/publication/279648904
Had a quick read of it and it didn't mention any water movement in the containers so I take it there wasn't any. So with diffusion being so slow in water I assume we can so for all practical purposes it doesn't take place unless the water is moving, but in our tanks the iron in the water column is being moved about due to our flow/tankturneover so the FeEDTA may/will degrade faster because of the flow and getting exposed to a higher PAR bombardment at the surface
another graph comparing FeDTPA and FeEDTA
Source
William Miller
I've mixed in dpta to my micro mix and it isn't pink at all, more dark orange which doesn't discolour the water that much. I
assume most people in the uk live with hard water with parameters probably close to mine.
Do you just dose full EI on alternate days with the edta iron in the trace mix?
Do you supplement with dtpa aswell?
Do you dose more than you need to because of hard water?
Do you add trace/iron more often than EI calls for?
I made up my own custom trace mix then added
Solufeed Fe 11 DTPA (1ppm (17.86 μmol/L) iron can be achieved by adding 9.5gramsof Solufeed Fe 11DTPA per 1000L of solution.) so 9.5g per liter yeilds 1000ppm add 100ml to 500ltank yields 0.2ppm Fe per dose, three times a week yields 0.6ppm weekly dose
But
Yes, watch the plants, it works.
I also found the FeDTPA doesnt discolour the tank much at all compared to FeEDDHA
I still was getting
So I started dosing some FeEDDHA manually on micro day - the above pic was post adding the FeEDDHA hence the green being back in the new growth.
Think the FeDPTA was breaking down either in the micro mix or by the light. I even light insulated my micro ferts dosing tubing.
The pale new growth has since returned again !
I have however decided to stop dosing LC (Liquid Carbon) as I dont think the tank needs it and have been reducing the dose slowly till the LC ran out. Have know setup my auto doser with FeEDDHA so I can dose it separately from the custom Micro mix and adjust it too suit the plants needs.
Was also planning (this weekend) to do a Micro mix without any Fe in. Then adjusting the FeEDDHA dose so the tank has a slight pink tinge for the rest of the photoperiod of Micro dosing day
Havent tried it using the STD EI Fe EDTA micro mix and adding FeEDDHA as a supplement. My tank was fine with STD EI Fe EDTA micro mix for the first 18 months and my water is hard to very hard.
So still work in progress and watching the plants
Hope it helps