[KrangDog]

I saw a thread about this from 2018, but there didn't seem to be a solid answer.

I currently mix my macro solution using RO water, KNO3, KH2PO4 and K2SO4 with a little ascorbic acid and potassium sorbate. The solution starts off colourless, but turns brown progressively over a week or two.

I'm not really concerned what colour the solution ends up, so long as the nutrients are still in an available form. Anyone have any comments on whether this colour change has any effect on nutrient availability and form?

 

[Deanna]

I have two 300ml clear reservoirs, for auto-dosing feeds, that hold various mixes of macros and micros (avoiding those combinations that may cause precipitation) and I use ascorbic acid and potassium sorbate in both. These supply for 30 days and I have yet to see any discoloration (other than the micros, due to iron, but it remains consistent in color).

Those three salts you mentioned should cause no discoloration issues.

 

[KrangDog]

Those three salts you mentioned should cause no discoloration issues.

Hmmm, it’s very consistent for me. Perhaps I’ve got a contaminant. I mixed up a solution of KH2PO4 recently and it turned a slightly brown colour too. Also used ascorbic acid and potassium sorbate in that. Maybe I’ll try mixing a solution of just the ascorbic acid and pot sorbate and see if the same happens.