Review on Level Up Your Aquarium: The U.P. Aqua Co2 Indicator Unveiled by Kendra Johnson

Flipping the display takes some time but you will get used to it over time. If you add a little more water above the fill line, you will lose some liquid when turning, but it will still stay on the line. The suction cup is not very good, you have to press it against the glass of the tank every few days. This solution seems to work for a long time. I prefer to change every two weeks. Also, I messed up the 4k solution for me which was the hardest part, but this product doesn't say you have to have 4k. He suggests using tank water, so it's up to you. After two months I can say that this product really works and gives me confidence that my CO2 level in my tank is at the optimal level.