will work for fresh clear water but if you try to test water with your nutes, molases, etc....it wont. once you add nutes to the water it changes the color of the water, in turn changing the color of the test water with the drops in it. you need a ph pen to test nuted water or run off water from your pots.
Where would i get my hands on one of those and how much.. i cant order any thing off the net right now and im not using any nutes for the time being so could it still work lol
most garden shops, home depot, lowes....they're not that uncommon. your link there is what alot of people start with because its cheap. only issue is if you have a problem you have to test the run off from the drip tray. Works great just to test your tap water, or bottled water that your starting with. but it works on matching a color spectrum so if the water you add the drops to isnt clear it throws off the results. you dont really want to skimp on a ph pen. the cheap ones arent entirely accurate but you can find em for under $15.