Use new growth on the water sprite (h. difformis) as an indicator
for low Fe (iron) and dose CSM+B or another product accordingly.
It will grow in pale if low on Fe. The only real wild card in all
this is K+ (potassium) since there isn't a reliable
hobbyist-level test kit. Look at the posts earlier this month on
K+/potassium to see what people are doing. I do a weekly 20%
water change, test for NO3 and PO4 then dose KNO3 and monosodium
phosphate (Discus Buffer)accordingly to get to the recommended
levels. If NO3 doesn't drop much during the week, I'll dose K2SO4
for K+ at about 5 ppm. It's looking like a twice weekly dose of
CSM+B at .1 Fe is working.