Water soluble micros needs low pH?

I've come across a Swedish reference on the subject of how one should mix water soluble micronutrients (like CSM+B). It says the chelates are rendered useless if one try to mix micro-powders with ordinary tapwater. The chelates breaks down before they come in contact with the metal-ions if the water pH is above 4-5.

I use a micronutrient-powder called "NutriSi" (almost exactly like CSM+B) that has 50% EDTA and 50% DTPA iron. I get iron-deficiency-symptoms even if I dose the equivalent of 1 ppm Fe (10 times the recommended 0,1 ppm) several times a week. I roll it with tapwater (pH 8, KH 2, GH 3, Ca 22 ppm, Mg 2 ppm), but after this I think I will try to get some citric acid to lower the tap to pH 4 before I mix it with the powder.

Would it suffice to use distilled water or do one need to use some kind of acid also?

I will cross-post this message at the APD also.

 

Re: Water soluble micros needs low pH?

I knew that question would be brought up, but it seems the actual chelate need to bind in an acidic environment (ph 4-5) to the metals in the powder. When they are bound they can stand the pH:s of our aquariums, especially the DTPA-chelate.

 

Re: Water soluble micros needs low pH?

Exactly, the chelate will not "trap" certain highly reactive trace metal cations if the pH of the solution-water is above 4-5.

When the chelate has trapped the highly reactive trace metal cations the actual solution will have become, for example, DTPA/EDTA-chelated iron - which is less prone to oxidizing and is usable in a wider range of pH:s.

I've already made a new batch with 300 ml battery water and 1.5 tsp Citric acid (which rendered the water a pH of about 4.5) and then I mixed in the NutriSi-powder. The result is already obvious in that the old tapwater-based solution is blood-red and the new one is brown.

So it certanly is a big difference, and I will see if some of my pale new shoots will retain a more lush green color with the new solution.

 

Re: Water soluble micros needs low pH?

At least EDTA is used to measure Ca+Mg so if you have the EDTA-powder and mix it with ordinary tap-water it will react with the Ca+Mg right?