[Wasserpest]

Originally Posted by DarkCobra

I don't know if you've solved the fungus growth in the trace solution yet, if not here's some info. All of this is taken from original discussions about PMDD on TheKrib's website.

To prevent fungal growth, add 0.5mL 9M HCl (hydrochloric/muriatic acid) per 300ml H2O. (Source link)

Thanks for the tip. Before I start messing with concentrated HCl, I want to try my luck with Seachem Excel. In another thread I read that the ingredient in Excel is otherwise used as a sterilizing agent. So that MIGHT do the trick, and improve plant growth along with it.

Originally Posted by DarkCobra

EDTA, the chelating agent used on iron in the trace mix, is known to be photosensitive once in liquid solution, and is best kept in the dark. Another person made the comment that at pH above 7.0, 80% of FeEDTA will decompose after two weeks. That may be another good reason to use the HCl! (Source link)

I am using Flourish Iron... not sure if the gluconate is more or less light sensitive.
I have used the half-transparent milk bottles to better see the level during the two week dosing period. Now I am more confident that it works well, need to find some cover for the bottles. Maybe just a black plastic bag will do.

Interestingly, while there is some (minor) growth in the traces bottle, the smell of it after two weeks is still similar to a new solution. On the other hand, the NPKMg solution smells like old wet socks after two weeks. Not sure what that's all about.