CO₂ long-term test

Aquatic plants need carbon dioxide, while fish and invertebrates only tolerate a limited amount. The range between too little and too much is narrow, and it shifts over the course of the day. The Dupla CO₂ Long-Term Test makes that range visible, not only at the moment of measurement but continuously.
The principle is simple and reliable. The bubble cap is filled with approx. 1 ml of aquarium water and two drops of indicator reagent. Fixed upside down to the pane, an air cushion sits between the aquarium water and the indicator liquid. Carbon dioxide passes through this cushion and changes the colour of the liquid. Blue means too little, green the optimum range, yellow too much.
The reflector cap rotates through 360 degrees, so the test is easy to read from any angle. The enclosed colour scale is attached to the outside of the pane right next to the test, which means you always compare under identical lighting.
Within a carbonate hardness range of 4 to 8 °dKH, a green colour corresponds to a CO₂ level of approx. 6 to 25 mg/l.
The indicator reagent is a purely aqueous bromothymol blue solution and is not classified as hazardous. Refills are available as Dupla CO₂ Long-Term Test Refill, item no. 80415.

Product benefits at a glance:

• continuous display instead of a single measurement, readable at any time
• clear colour change: blue too little, green optimum, yellow too much CO₂
• optimum range of approx. 6 to 25 mg/l CO₂ at 4 to 8 °dKH
• reflector cap rotates through 360 degrees for easy reading from any position
• leak-proof indicator liquid, attached to the inside pane with a suction cap
• alcohol-free indicator reagent, not classified as hazardous
• refill reagent available separately, item no. 80415

Setting up the test:
1. Before first use, pierce the protective film in the dropper with a needle.
2. Disassemble the test and fill the bubble cap with approx. 1 ml of aquarium water up to the marking.
3. Add two drops of indicator reagent.
4. Press the inner part of the reflector onto the bubble cap and make sure the O-ring is correctly fitted.
5. Turn the bubble cap over and fit it into the lower part without losing any liquid.
6. Attach it to the inside pane with the suction cap, the lower part must be immersed.
7. After approx. 10 minutes, read the result against the colour scale attached outside.

Good to know:
Replace the indicator liquid after every water change, at least every 14 days.
The test is meaningful within a carbonate hardness range of 4 to 8 °dKH.
With CO₂ systems without night deactivation, read shortly after the lighting is switched on, as the level is highest then.
Grease the O-rings lightly with silicone grease from time to time, item no. 80397.
Protect the test from algae growth and clean it with clear water when required.
Suitable for freshwater only.