Hi there. I'm currently using liquid carbon but as soon as this bottle runs out I'm going back onto a pressurised cylinder. Now years ago I used co2 and I had a drop checker. I never really liked using it and used a ph and kh test kit instead to estimate co2 values. Now I realise I was doing it all wrong. Apparently the co2 needs to be on 2 hours before lights on and go off 2 hours before lights out. Maybe this is why my drop checker always looked yellow even though the ph was approx 6.5 to 7. Seeing that a drop checker is really just an in tank ph tester rather than a co2 tester I was wondering if most people use one or just not bother and use a normal ph test kit instead?