What youā??re experiencing is your tap water outgassing.

Iā??ll take a wild guess in that your water is likely well waterā?¦.at least water that hasnā??t been exposed to the air for long.

Outgassing isā?¦.de-acidification. So as the water outgases (de-acidifies) the Ph can only rise.

When I do a res changeoutā?¦.I must correct for the rise in Ph for at least 36 hours.
Airstones accelerate outgassingā?¦and I use a lot of air, so longer than 36 hours is certainly not out of the question.

Hope that helps,
HMR
Horsemanrocks Reviewed by Horsemanrocks on . Ph altered water reverts back over time? Hi everyone I just have a quick question I wanted to ask since I've searched loads of ph related threads but not come across the answer and I'm curious. I put in my PH down into the tapwater (tapwater is PH 8) that had stood open airing for 24hrs and checked the reading with my little aquarium strip tester - the result was clearly in the 6.5 PH colour. I watered my baby seedlings and then as there was still water left over I continued to use this water over the following days. When I Rating: 5