How much co2 for a planted tank? Do aquarium plants need CO2?

Deciding to go with injecting CO2 can be quite the decision and can seem daunting. So, let’s go over some variables you should consider and how to use CO2 in an aquarium.

Get the proper gear

Drop checker

Before we begin, let’s make sure that you have the proper gear. So, you have a source of pressurized CO2 but did you buy a Drop Checker? This is how to measure CO2 in aquariums. A drop checker is one of thee most essential pieces of equipment when it comes to being successful with CO2. It’s used to gauge how much CO2 is dissolved in your water column. 

Second, be sure you have a Bubble Counter. This will be used as a unit of measure of how much CO2 we are injecting  into our planted tank. 

The Bubble Counter

As a rule of thumb, for every 5 gallons of water, you should have 1 bubble per 3 seconds. So for example, for a 5 gallon tank, 1 bubble every 3 seconds. For a 20 gallon tank, 4 bubbles every 3 seconds. Now, remember that these are just recommendations and you should have a drop checker in place to give you a more accurate reading of dissolved CO2.

The Drop Checker

Okay so now you have your drop checker, now what? Well, you gotta learn how to read it! First off, read the instructions and fill the indicator liquid properly into the drop checker and submerge it into your tank. The color of the drop checker liquid will initially be a deep blue color, this color basically means NO CO2.

But, consider that the liquid is fresh out of the bottle and will take a few hours to get an accurate reading for your tank. As the indicator fluid reads more CO2 from your tank it will slowly shift from deep blue, blue and to your target color…forest green!

Forest green

This is the magical color you will aim for, this basically says that you have enough CO2 for your plants. After forest green, it will near a yellow spectrum. This means that, as the indicator fluid nears yellow, this will indicate that you may have too much CO2.

The yellow danger

Now, you don’t ever really want to be in yellow because, you will be in the danger zone of suffocating your fish! Please note that green-yellow is not a bad place to be if you know your plants are using up a lot of CO2. But, do take the green-yellow color as a warning of imminent yellow danger. Because the indicator fluid takes a couple hours to show a true reading.


You may be wondering do I need CO2 for aquarium plants? Well, it depend on how much growth you desire. Because not only will the rate of growth be greatly increased but also the quality of the plants themselves. 

So, remember the 1 bubble per 3 second per 5 gallons of water rule. Also, be mindful of the color of your drop checker and consider that it will take at least an hour to give an accurate reading. Consider forest green your magic color and green-yellow a warning sign to cut back on the CO2.

How much co2 for a planted tank
Article Name
How much co2 for a planted tank
Let's figure out exactly how much CO2 your planted tank needs by utilizing some essential gear such as a drop checker and bubble counter.
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The Good Algae
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