Test Results

For pH run a glass of water and test it straight away. Then let the water sit somewhere overnight and test it again.

GH 7 drops = 7 dH and 125 ppm
KH 4 drops = 4 dH and 72 ppm

The table in the API instructions is range bands they suggest for certain fish. To find the GH & KH in ppm, multiply the number of drops by 17.9. There is a table at the end of the leaflet as well for converting to ppm.


Hardness is always GH. This is the amount of calcium, magnesium and a few other metals in trace amounts. GH is the one which affects fish directly.


(KH is the amount of buffer in the water, usually carbonates and bicarbonates. Buffer is a chemical term meaning something which stabilises pH. It affects fish indirectly. The natural tendency of a fish tank is to become more acidic. But KH buffers the water against changing pH. If there is not much KH it gets used up then there is nothing to stop the pH changing. If KH is high, there is a lot of buffer and if we add chemicals to change the pH, it will change initially then the KH will being it back to what it was.
So with low KH there is a risk of the pH dropping very quickly and with high KH if a pH changer is used the tank has yoyoing pH. Neither of these is good for fish.)

Some people say you can put tap water in a container and shake it vigorously for 5 minutes, that would make my arm fall off 
Leave it to stand for at least 12 hours.

pH is the only thing which can change on standing so that's all you need to test in water that's been allowed to stand.

Carbon dioxide dissolves in the water in the pipes. CO2 makes the pH drop. Leaving it to stand allows the CO2 to gas out of the water so the pH rises.
In very soft water areas, water companies sometimes add chemicals to raise the pH to stop acidic water corroding the pipes. In this case, the chemicals gas out and the pH drops.

Usually the change is only small but ti's still worth checking just in case your water is one with a larger change.

Well the PH never changed. Still 7.4 after 12 hours.