 Re: is there any adverse effect of kh being low?
Presuming you fert, low KH doesn't cause issues with most species of plant. Low KH and CO2 still keeps people at 6pH and up quite often, which is great for many plants. There are a few species that will prefer harder water, but these tend to be the exception.
In my opinion, pH controllers aren't all that great of a thing. It's consistent CO2 that you're after for plants, not consistent pH. For fish, you want consistent KH; consistent pH from CO2 isn't a big deal. Over 95% of the CO2 you pump into your tank isn't going to turn into plant, and I can promise your concentration of H+ is going to vary more than +/- 2.5% without even accounting for calibration and localized variances. I know it's something you probably don't want to hear after spending the money, but would you want to keep it if it's making it more difficult for you to achieve non-limiting CO2 levels?
-Philosophos | 
Hybrid Mode
