Increasing potassium for my Pinatifida?

[Larry Grenier]

Plants are mostly doing OK, not good, just OK, in my new planted tank except the Pinatifida. I've read a few places that adding potassium is sometimes a fix to the problem. My question is what form is best; K2S04 (Potassium Sulfate), KN03 (Potassium Nitrate), or KH2P04 (Mono Potassium Phosphate).

Here's how I'm mixing my Macro Mix which I add twice/week and micros once/week.
1.5 parts K2S04 [K], 1 part Ca(NO3)2 [Ca+N], 1 part KN03 [N+K], .5 parts KH2P04 [P+K], .5 parts MgSO4 [Mg]

I just started Compressed CO2 and will be setting-up my drop checker this weekend.

Note: I'n not a chemist and historically, a brown thumb.

Thanks

[Larry Grenier]

I'm thinking K2S04 (Potassium Sulfate)

[krisw]

Yes, K2SO4 will add potassium without throwing off the balance of Nitrate/Phosphate.

For me, I combine the three in the following ratio and dose dry:

6 - KNO3
2 - KH2PO4
1 - K2SO4

That seems to be a good mix for most things. Adjust phosphates up/down depending on the amount of nitrate in your tap. Basically, start with my ratio. If you get green spot on glass, up the phosphate a bit until you no longer get any a week after cleaning it off.

[Larry Grenier]

Thanks Kris... How did you know I has a GSA problem too

[krisw]

Heh -- that's one of the handful of tell-tale signs to look for in terms to nutrient imbalances. It's not uncommon to see.