Filling a co2 drop checkerSome assistance
For the monitoring of the CO2 content in a planted aquarium a long-term checker (usually referred to as Drop Checker) is used. This is filled with a CO2indicator fluid, which shows the CO2 saturation by a colour change. Blue means too little, yellow too much and green just right. Please note that a reaction of the indicator liquid and a corresponding color change is often delayed by several hours.
The indicator fluid should be replaced every 4 to 6 weeks, to keep the drop checker working properly. At the latest the fluid should be replaced if it loses colour and turns more transparent.
Most common glass drop checkers are comprised of a spherical head that is filled with indicator liquid. A curved connection bridges the glass sphere to a funnel-shaped inlet with a convenient mount for the required suction cup. With that suction cup the drop checker can be easily stuck anywhere to any aquarium pane. During set-up it needs to be taken care of, that the drop checker has the inlet pointing downwards, the funnel needs to be filled with air, not water. The CO2 diffuses from the aquarium water through this buffer of air and subsequently reacts with the CO2 reagent in the spherical head. Should the indicator fluid get into direct contact with the aquarium water, the colour change usually happens immediately. Furthermore there will be a falsification of test results because the carbonate hardness of the aquarium water influences the indicator fluid, too - thus direct contact with the water is to be avoided.
A pipette is suitable for filling and emptying the orb. The pipette is flexible enough to be able to reach the glass ball through the curvy neck of the drop checker.
For filling purposes, the drop checker is held with the inlet pointing downwards. Now some reagent is put into the pipette and filled into the orb head of the drop checker.
Overview of available models
Apart from the already mentioned drop checkers made of glass, other variations are available, too.
So-called Hang-On Checkers are just hung over the rim of an aquarium pane without using a suction cup. These are especially good for open tanks with a pool set-up. Due to this design, even less technology can be seen in the aquarium.
The Double Check v2 from Cal Aqua Labs is equipped with two spherical heads. The upper one works conventionally, whereas the bottom one is filled with a reference liquid, making it very easy to compare colours and adapting the CO2 content even better.
Spherical models such as the Orb Checker are characterized by an inside opening. Their design is thus even more compact and the reagent can be read especially easily.