Drop – CO2 tester

Want to find out the CO2 level of your tank? Then hang this CO2 tester in your tank. Combined with the PlantedBox indicator mix, it will be a breeze to determine the CO2 in your planted aquarium.

  • Measure CO2 quickly and easily
  • Better CO2 means healthier plants
  • New & more elegant model
  • Easy & quick to clean
  • Free advice through the blog, ebooks & mail

The Drop CO2 tester is great for all types of aquariums and easy to read. A must-have for every planter.


In stock

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Made of strong glass

Gemakkelijke setup

Easy to measure CO2

Elegant model

Elegant model

Measuring CO2 with a drop checker

Don’t know how to measure the CO2 in your planted tank? Try this CO2 tester or “drop checker”.

You just need to add drop checker indicator mix to the CO2 drop checker and wait. After a few hours, the liquid will turn a certain color. Blue means you have too little, yellow too much and green is just right. Easy, right?

PS: you can also order the mix and the drop checker as a set, which saves a few euros again.

Made of sturdy, clear glass

Did you know that this CO2 tester is handmade from sturdy laboratory glass? This makes the glass extra strong, making it less likely to break. Because that would be a shame, wouldn’t it?

Plus, the glass is nice and clear so the focus is completely on your aquascape and not the technology!

Free advice for you and your aquarium

Need advice? Read one of my many articles on the blog or download my free e-books.

hoe werkt PlantedBox


How do you place this drop checker in your aquarium?

1. Turn the drop checker upside down
2. Add a few ml’s of the indicator mix to the drop checker
3. Hold the drop checker at an angle and tap the edge with a finger so that the liquid enters the “bubble”
4. Now turn the drop checker over & place it in your container

When do you know you have enough CO2?

This is actually quite easy. Just look at the color:

  • Blue: too little CO2. Carefully (!) inject some more CO2 into your tank.
  • Green: OK, but a little more would be better
  • Lime green: OK
  • Yellow: too much! Add less CO2 or put more oxygen into the tank

How to clean the drop checker?

Replace the indicator mix at every water change. Just turn the drop checker over & rinse it out with RO water (not tap water, as it may affect the result!). If necessary remove algae & clean the suction cup with some filter wool so it adheres well again.


Customer Reviews

Based on 30 reviews
Luc Mees
Goed product

Is reeds mijn 2de en ben er tot hiertoe goed met geweest

Alain Vrijdag
Mooi product

Werkt zoals het hoort en mooi om te zien ondanks tegen de ruit van aquarium.

Chris Vannieuwenhuyse
CO2 tester

De CO2 tester van PlantedBox is echt een aanrader. Gemakkelijk in gebruik en onderhoud. Nu weet ik tenminste of ik met mijn CO2 goed zit of niet.

Steven de Bruijn
Prima dropchecker

Drop checker en All in one planten voeding besteld en ook nu weer heel snel geleverd. Prima Gilles

mario rouzee
Drop-co2 tester

de drop-co2 tester werkt perfect.Gemakkelijk te plaatsen in het aquarium en het oogt mooi en de service is ook top thx Gilles