Actually, there are several people running these higher levels of CO2
with a KH
just as low, if not lower, than yours. Some of the risks that people where afraid of have proven to be less likely than originally thought. The biggest problem is that people who don't have a pH controller, often don't have a good way to measure the pH to ensure that they are getting the desired levels. There are a couple of ways around this. They can buy an inexpensive Pen pH Tester or construct a CO2
Drop Checker. The one allows you to read lower pH levels than liquid test kits, while the other allows you to test the CO2
levels with a set KH
that is different than the tank. I wouldn't mess with your KH
if don't have another reason that you would need to.
Also I'd adjust your meter so that it doesn't dip below 30ppm. It's fluctuations below 30ppm that encourage BBA. If you keep the levels about 30ppm, then the fluctuations won't encourage BBA.