
Just remember it is the ups and downs of ph that are hard on fish.....
To mess with your ph means you ALWAYS have to do it, and keep it in your tank maintenance program....
If on the other hand you let your fish adapt to the ph you normally have, they will be healthier over the long term, because as you do water changes, that ph won't be fluctuating all the time.
This works for most fish. Some will HAVE to have a certain ph. I believe discus are an example of this. So do your research on the fish you want to keep, and decide if you have to have one of those kind that NEED a ph under 7.0 for example, you can have a tank just for them, and cut the ph problem to just that one tank.
As sirdardsol stated, peat in the filter can help lower ph, though you have to change this periodically, another option is to add lots of driftwood to the tank decor, as this tends to lower ph also, but more slowly and safely than chemical means.
If I had a discus tank I would set it up with a drip RO system that constantly runs new RO water into the tank.....but that is when my "ship" comes in and I have unlimited $$$
