Bulb – CO2 tester

Suffering from algae or poor plant growth? Probably you are not adding enough CO2. The “Bulb” drop checker helps you determine and improve the CO2 in your tank.

  • Easily measure CO2 levels in your aquarium
  • Slightly larger in size so ideal for large tanks
  • Clean & refill even faster
  • Nice and clear readout
  • Free advice via the blog, ebooks & mail

The Bulb CO2 tester gives you more control over the CO2 in your aquarium, allowing you to further improve the health of your plants.


In stock

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Made of strong glass

Gemakkelijke setup

Easy to measure CO2

Grote aquaria

Ideal for larger tanks

Wat is this product?

Is your tank overgrown with filamentous or bearded algae? Or your plants lack color, seeming to fade more and more every day? Chances are you’re running low on CO2, which is one of the most important nutrients for your aquarium plants.

But how do you know exactly how much to add to prevent growth problems and algae?

Sounds difficult, yet it doesn’t have to be. This “Bulb” CO2 tester shows in a very simple way whether you have too little, too much or just enough CO2 in your aquarium.

Super easy measurement of your CO2

“So how can you determine the amount of CO2 with this drop checker?”, you’re wondering now?

The operation is actually super simple: first you add the indicator mix and then you turn the Bulb over. Finally, you hang it somewhere in your aquarium and about 1 to 2 hours later you will see that the color of the indicator mix changes.

  • Is the drop checker blue? Then you have too little CO2
  • Is it green? Then your CO2 is good
  • Rather yellow? Beware, you probably have too much CO2

Pretty handy, right?

Large aquarium? Then the Bulb is ideal

I sell several CO2 drop checkers, including the Drop and the Clip. But which one is the best one for your aquarium? Well, if you have a large aquarium (say 200 liters), the Bulb is surely the best choice.

Why? It is larger than the other 2 models, making it much easier to read the CO2 reading. Even among all those healthy aquarium plants!

Need advice?

Want to get your CO2 on point? Or crack down on your algae? Download one of my e-books and you’ll receive tips and coaching tailored to your aquarium or read my articles on the comprehensive blog!

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How do I best install my Bulb drop checker?

1. Turn the Bulb over, you now see the opening
2. Add the indicator mix
3. Carefully turn the Bulb over & place it in your aquarium

How do I know what my CO2 level is?

This is super simple, you just have to look at the color of the liquid:

  • Blue color: too little CO2, carefully add a little more CO2
  • Green or lime green: OK
  • Yellow: you are adding too much CO2, be careful with your fish!

How should I clean the Bulb drop checker and when?

This is best done with every water change. Just rinse it out with RO water, run the filter wool over it and refill. I do not recommend using tap water for rinsing because you may get wrong color reproductions due to the calcium in the water.


Customer Reviews

Based on 19 reviews
Alain Vrijdag
Bulp voor co2

Heel mooi van vorm en indicatie van kleur co2 is correct.
Snel geleverd en goed verpakt.
Ik ben tevreden.

Gerrit Hagen

zeer goed ben zeer tevreden

Bedankt Gerrit!

Gilles van PlantedBox

Danny Bachor
Bulb-co2 tester

Ik had voor mijn grote 200 liter bak een grotere co2 tester nodig en deze is perfect en goed leesbaar en een mooi formaat voor mijn bak

Frank Bolland
Stijlvol en nuttig

Deze Bulb CO2 tester ziet er erg fraai uit in mijn Juwel Vision 450 en ook goed af te lezen. Goede aanwinst voor mijn aquarium.

Bedankt voor de review Frank, leuk om te horen dat je tevreden bent!

Erwin G.
Handig in gebruik en goed

Handig in gebruik en goed leesbaar van co 2 waarde