im just using the cheap ph test kit where u add like 4 drops of a solution and it turns the water a certain color. probably isnt perfect but it works.
i know you can get a kit for less then 20 bucks on ebay, amazon, etc with ph up, ph down, and a liquid test kit.
http://www.amazon.com/General-Hydro...KWZY/ref=sr_1_1?ie=UTF8&qid=1314552091&sr=8-1
Very nice. Its making me want to smoke.. My vertical growth is slowing on my older plant also. How many tops do you have?