OK....I did the aeration test. I have good news and bad news.
The good news is, almost like magic, the PH did come down from 9.5 to 8.O. Also, the PH drop appears to be permanent. After turning the air off last night, I checked it again today and it remained at 8.0.
The bad news is, it took 4 hours of aeration to get down to the 8.0 reading. Perhaps the long length of time is due to the initially high PH, as well as the low KH value. I've turned the air on again today to see how much longer it will take to get near a 7.0 reading that my tanks are.
I do like the idea of this method since no chemicals are involved. One of my concerns is ramping up this method to a 32 gallon trash can full of water. With my current air pump, I'm afraid it won't push enough air to be effective.
I do have a fairly powerful submersible water pump. I wonder if this might be as effective as a air stone. Is water movement the key, or are air bubbles needed for this.
My other concern is that my two largest tanks are in my living room. I will have to leave the trash can with pump running for a fairly long period of time. God forbid if I leave it running while I go to work and the can springs a leak. There goes my paranoia again :aah:
I also did another experiment. As lanstar
Baking soda "wants" (read ion balance) the pH to be about 8.5.
I took some of my 9.5 tap water and added some baking soda. Instead of raising the PH, it did indeed lower it to 8.5. How much I put in did not matter, the PH remained at 8.5.
I may trying using a combination of aeration and baking soda. If I do, I'll only add enough soda to get to the 8.5 reading, and let the aeration do the rest. Even if my KH and PH goes up some, it shouldn't be a problem as long as its gradual. I may even end up with a more stable tank when in comes to PH swings.
125gal planted tank, natural gravel substrate(small grain), Eheim Pro 2028 canister filter, 6 30 watt fluorescent lamps(1.44WPG), no CO2, no fertilizer, angels,guppies,cardinal tetras,.