The most accurate and cost effective way of understanding the kH value of your aquarium which is effected by C02 levels.

This solution (accurate to about 0.01ppm KH) can be used with all drop checkers and the solution is laboratory tested - this means no more guessing or being unsure.

In order for this solution to work correctly, it requires bromothymol blue which reacts with the 4dKH solution and changes colour according to the amount of C02 in your tank.

If you would prefer a premixed version with bromo blue already added, search for model number 4dkhB.