Significantly better than stationary green / blue permanent testers but a little more difficult to use

use many JBL products quality as expected supply and price also. Find ich sometimes a bit overpriced because the content in chemical terms probably 20Cent is worth but is just too difficult to itself the right to set a molar ratio.
This test is a bit more complicated because you have to test twice, so a "blank measurement" of degassed / geschütteltem / boiled water aquarium and a "full measure" with fresh AQ water. Difference measurement gives real CO2 content.
The color change occurs only at low CO2 held held from 40mg / l inerhalb 1-3 drops in CO2 also increases the error and may ever act to 5-6 drops. Until you sure that's the color corresponds to the test field.

Has mans mall out there is but an order of magnitude more reliable than the blue / green permanent test in Auqarium!