ASA Hang-on Glass CO2 Drop Checker

A hang-on glass CO2 drop checker is a specialised tool designed to monitor dissolved carbon dioxide levels in planted aquariums. Unlike traditional internal checkers that rely on suction cups, this variant hooks directly over the tank's rim to keep the indicator bulb suspended outside the tank or along the glass rim. This clever layout keeps the glassware free from unsightly algae build-up while reducing visual clutter within your aquascape. 

The device operates via an internal indicator solution (not included) that changes colour as CO2 gas diffuses out of the water, crosses a trapped air pocket, and blends into the fluid.