It is never easy to respond to a question like this. So, I will just say, no, I have never had an "ionized water filter", nor has anyone else, to my knowledge. Water is H2O, and it doesn't exist as "ionized water". If you add a salt to the water, the water contains ions, but pure water is not ionized. You can't adjust the pH of water with an "ionized water filter". http://www.chem1.com/CQ/ionbunk.html
Well i found the filter in my kitchen. Apparently my parents had bought it a long time ago. I set the filter to 6.8 and then I tested the water that came out. It was 6.8 but I've heard that the water isn't safe for aquarium use. Can anyone verify this?