I keep hearing about pH testers. Will a basic pocket pH meter like this on (http://cgi.ebay.com/Digital-pH-TESTER-Hanna-CHECKER1-hydroponics-nutrients-/380223631624?pt=LH_DefaultDomain_0&hash=item5887183108#ht_5677wt_994) work? I dont want to break the bank, but I am a beginner. What works for you?