DWC pH Help

I have my plans layed out and everything but my only concern that I kinda don't understand is the pH. I understand that the resevoir should be around 5.5-6.4, But how do I keep the pH level even? Do you add water, nutrients AND stuff to keep the pH balanced? If so, can someone explain to me how to keep it balanced and what to use?

I have a pool pH testing kit at my house, would this be a good enough tool to test the pH of my resevoir water in? When I test the water in the resevoir and the pH is to high or to low, what exactly would I do to raise or lower the pH, that's what I'm getting at.

There are pH up and down adjustment products. Get one made for hydro not aquariums or pools. A digital pH meter is well worth it, you can get one on ebay for about $30. You don't try to keep pH level, just in a range. Ideal is 5.8 but drift is ok from 5.4 up to 6.5 or so.

As for water, start with reverse osmosis water for fewer problems later on. pH adjust it going in to your res and then add nutes mixed in water and pH'd. There is much more around here on pH.