In my exerience, it's better to keep the water stable, rather than trying to "fix" it. I've kept rams many times in what I like to refer to as "liquid concrete"-- tap water with a pH around 8 and very high KH and GH levels. Granted, I did have to use distilled water to soften it a bit for breeding purposes. As long as the water quality is kept high, I wouldn't be too concerned with trying to alter the chemistry, unless you're dealing with wild-caught specimens.