Hi guys/gals.

we have recently est up a 360ltr tank, I call it 300 ltrs with all the gravel, plants & driftwood etc. I have a UV filter. Make my own RO water etc. the tank is approx 2 months old. We did the cycle and didn't lose any fish to it.
Looking at water quality.
Nitrites 0, Amonia 0, Nitrates 15-25. GH 16 degs, KH started at 6 degs but with using RO water falling slowly. PH around 7.

My main question to raise the KH level. I have red about bicarbonate but don't want to raise the PH level.

So I'm think potassium carbonate as from what I read this will raise the KH level for better PH buffering but not raise the Ph itself. how ever I can't find any thing on how much of this stuff to add to the tank and how much difference it will make to the KH level. Any ideas?

I read some folks are happy to have a KH of 2 but in general most seem to disagree with this as the ph swings then can just yoyo.

This is a heavily planted tank, If I knew if and how you can post pics I'd put on up.

Regards Karl