I take water sample weekly for the free testing the local store offers. My hardness is about 200 ppm. I'm also injecting C02 (yeast generator) and using a canopy as a water/C02 reactor. This week's test showed a pH of 8; the goldfish don't seem to mind, but I'm worried about the weather loaches. I didn't add buffer last water change, and the C02 rate hasn't decreased, so I don't know what could have caused this. The tank is at about 6 weeks. For the last couple of weeks I've started turning off the air diffuser during the day, as several sites say that air diffusers disturb the surface too much and C02 loss is too high; I've a lot of plants and they've grown very fast since. The fish don't seem affected by the lack of bubbles, so I'm assuming they get enough oxygen...is that a safe assumption? Most importantly, what do I do regarding high pH? I've read that adding acids will just deplete the buffer but not decrease pH in the long run. How do I set up things so that I have a proper pH and hardness together with a decent level of C02?

What was you original pH? The easiest solution to your problem is to increase the CO2 injection rate... Get a larger bottle for your CO2 reactor or use another one. The plants must have grown and they may be taking a lot of CO2. Word of caution, if you are adding CO2 you must buy a pH test kit. It is very important to monitor pH frequently (specially with yeast CO2 reactors where you cannot regulate the input). Always check pH early in the morning... that is when it is the lowest.

My pH had been mostly in the 7 to 7.4 range since I started the tank. Is there any way to maintain GH while reducing KH enough to lower the pH?
BTW I just bought an electronic pH tester with calibration solutions off eBay. Too bad I couldn't find any hardness meters under $150.