Pete, that statment about high numbered chems and worms applies for anyone. pH meters, The $20 ones are good for a couple years, I like the 2 probe types over the singles. I have a Kelway I paid about $55 it is more accurate but the probe itself is a little large. My Kelway I can interrpolate down to about .025 the 2 prong rapid test about 0.1. pH change is logarithmic Byron