i made a DIY carbon filter a while ago and was dissapointed, i found out that they use a different type of activated carbon than the stuff i was using from the pet store
i heard the hannah was good, i have a soil tester, and ph strips, but the strips are useless once you add nutes, so it sucks, i was thinking of just getting a cheap pool ph tester i think they are like 8 bucks but im not sure if it will work