I've never tested the ph of anything other than stuff in my college labs as I usually grow outside and when I did grow inside many years ago, we were to ignorant for that level of complexity. I do know that you are suppose to measure the soil run off. As in run some water through a pot full and then measure the run off. I also know that you need to get strips that are in the correct range. Most people seem to use aquarium testers.

I'm getting thirsty so I'm off to the club for a beverage. Hopefully someone with more experience with ph testing can help you out.

Again, best of luck,
CCF