Dave Spencer
Gort! Klaatu barada nikto.
Also pH helps judge how much CO2 there is in your water from a CO2 system...
Only when used with a drop checker that has a fluid of a known dKH. Otherwise, there are too many other factors in the aquarium affecting the pH.
...and can give a gross indication of KH.
I`m not sure what you mean by gross, but once again there are too many other factors in the tank affecting the pH to use it for measuring KH.
Otherwise, IMO, a lot of what pH is expected to show is really a function of GH but is not often recognized as such.
Possibly because this is not the case. GH is a measurement of Ca and Mg ions. I see what you are saying, but it is possible to have water with a high GH, but low KH (alakalinity).
I hate test kits because they are so general in what they measure. Hobby KH test kits don`t even measure the KH. All kits can give is an indication of a general trend, unless they are peoperly calibrated. Even then, we all mess up when taking the samples and readings.
I used test kits on my first ever tank, which give me the rough indication that a high light tank full of fast growing plants uses circa 5ppm of nitrates per day. Now I just observe my fish, plants and algae to give me a far more accurate (and confusing) idea of what is going on. For instance, my plants will tell me if nitrates are low, irrespective of what a kit says. BBA and staghorn algae tell me where the CO2 is low far more accurately than pH probes etc. I have even started to take the CO2 drop checkers out of my tanks as well.
I am going to put my head on the chopping block and state from my own experiences that the kits we use are a total watse of money! Buy something useful instead.
Dave.
Dave.