Hi mate, don't get the green 4 in 1 tester. I got it and its rubbish. Its saying my PH is 8 which I know for a fact it's not judging by my runoff 5.8-5.9 PH.
I think the best way to test without spending mega bucks is with runoff and a ph pen. I maybe proven wrong.. I hope so because I'll buy it 😝