Hello sean,
That's the exact pH tester that I use myself. Although I'm not sure if you know that once you test the pH, you will probably need to adjust it. The tester just tells you what the pH is. To adjust it, you need to use pH adjusters for that, using pH down if it was to high, and pH up if it was to low. General Hydroponics often sells the adjusters (pH up and pH down) along with the pH tester like this:
PH Control Kit (ph up&dwn & ph tester), General Hydroponics PH Up/Down, or separately like this:
pH down and
pH up. Along with the liquid pH adjusters General Hydroponics also makes
dry pH adjusters. I use dry pH adjusters by Earth Juice myself:
Earth Juice Natural pH up & pH down - Plant It Earth. I don't know about the GH pH adjusters (because I have never used them), but I know the Earth Juice dry Christal's last a long time. The one pound containers of each, lasts me well over a year.
As for other testers (EC/TD/PPM), they can be useful if you have an extra $100 to spend, but are not really necessary. Cheap and/or inexpensive ones will likely just not work well and cause you many problems anyway. In about 3 years now of growing hydroponically, I still have not bought one, or found a need for one.
As for the Go Box Starter Kit, that's a organic
nutrient line by general hydroponics. To be honest I have never used them, or have really herd much about them. But it looks like they are a complete set, and I found GH's feeding schedule for them:
http://www.generalhydroponics.com/ge...-FeedChart.pdf, and going by the feed chart it looks like all the components are in the kit. But there a couple of things to consider, first is that kit looks like everything except the GRO that is a 16 oz bottle, everything is only 8oz bottles. Again going by the feed chart and 10mL (2tsp) per gallon, that only comes out to 47 gallons of nutrient solution it makes at best (and that is the 16oz bottle of gro). If you have a 20 gallon reservoir that is only 2 nutrient changes, and if you changes your nutrient solution every other weeks, that's basically one months worth nutrient solution. Not even enough to grow the plant's to maturity.
As a new person to hydroponic gardening, you may not get good results from organic
nutrients. Organic nutrients are not completely broken down into the raw minerals the plants can absorb. They rely on micro organisms to finish breaking them down, and because of this, it's hard to really know what mineral elements are in the nutrient solution at any given time. PPM/TDS/ and EC meters wont be able to tell you either. In fact, I could be wrong but I believe due to the organic nature, the meters are not even very accurate with organic nutrients. But regardless they still cant tell you the levels of each individual mineral element of any nutrient (of any nutrient solution, organic or not), and that's where the issues with organic nutrients are.
You also need to be much more aware of how the plants are reacting to any change in the nutrient solution. There are a lot of components to that line of organic nutrients, and each preforms different functions. It's generally hard enough for new hydro growers to get used growing hydroponically, without adding the need to learn how to control the micro-biology of a living nutrient solution. It's very similar to aquaponics, just without the fish. In fact most of those components are used in aquaponics. So unless you really want to grow certified organic produce, I would suggest starting with regular hydroponic nutrient solutions (at least at first).