NANO CO2 indicator

This tiny CO2 indicator or "drop checker" - about the size of a thumb tip is made from crystal clear acrylic and allows you to easily monitor the amount of CO2 being pumped into your aquarium. 
 
It can be used in very small tanks without being obtrusive or placed in different areas of a very large aquarium to verify that CO2 distribution is perfectly even throughout your tank.
 
If you're using CO2 without a drop checker, you are essentially running blind. Use this indicator to make sure that you are providing your plants with enough CO2 and not hurting your fish and shrimp with too much.