05-14-2010, 08:20 PM
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If memory serves me, your water is quite hard, meaning the KH and GH are high. KH is what buffers pH and resists attempts to lower it. The harder the water, the less the effect of "natural" methods like peat and wood will be. I've never had to worry about this, having very soft water out of the tap, but if I did have this issue I would absolutely get a RO unit. It is far more reliable. Though initial cost is high, long-term you would need to buy a lot of peat to lower the pH significantly, and it wears out, faster the harder the water.
Now, having said that, if the angel fish are tank raised (most in stores are) they seem to manage with the pH in the 7's. And aquarists have them spawn; several memebers here have. Some fish are more adaptable than others. I'm not saying angels will live normal long lives in a tank with a pH of 7.8 or 8, but conversely I've no idea if it negatively affects them either. If you were dealing with wild-caught fish that would be a totally different matter.