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3 Signs of Too Much CO2 in aquarium (And 2 ways to reduce it)

In this article, I am going to tell you three signs that show that your aquarium has too much CO2.

Then I will also tell you a couple of ways to reduce CO2 in your aquarium.

3 Signs of Too Much CO2 in aquarium (And 2 ways to reduce it) image

So, what are the signs of too much co2 in an aquarium?

The short answer is fish behavior such as fish coming to the surface and gulping air very frequently. Or lethargy shows that your aquarium contains too much CO2. 

Besides, if the liquid in your drop checker turns yellow then it is a sign of too much CO2. 

3 signs of too much CO2 in aquarium

Now I will explain in detail the three signs of too much CO2 in the aquarium.

1. Fish behavior

The behavior of your fish can tell you if you are aquarium contains too much CO2.

But identifying your tank has low CO2 or not based on the behavior of your fish can be

tricky especially if you are a beginner.

This can be tricky because every species of fish has different CO2 tolerance range.

Besides, not all the fish in your aquarium will show the signs at the same time.

For example, bottom-dweller fish will show the signs of too much CO2 very early. Whereas the fish that usually stay in the middle or upper part of your aquarium will show the signs later.

Still, you can identify if you are aquarium contains too much CO2 from the behavior of your fish.

Gulping air

fish gulping air

The most common behavior in case of too much CO2 in your tank is fish will frequently come near the surface of the water of your tank and gulp air.

Why fish behave like that in case of too much CO2?

This is because when there is too much CO2 in your aquarium there is usually oxygen deficiency in your tank.

And by gulping the air, fish are basically trying to get oxygen from the air.

How to Increase Oxygen in Fish Tank? (8 Simple Ways)

Fish hanging around near the surface of the water of your tank

Gas exchange takes place in the upper part of your aquarium near the water surface of the water of your tank.

So, in case your aquarium has too much CO2, there will be oxygen deficiency. And the fish will hang out more near the surface of the water of your tank because there they will be getting more oxygen than any other place in your tank.

And this is the reason why bottom-dweller fish will show signs of too much CO2 early. Because if there is too much CO2 in your tank, the oxygen deficiency will arise early near the bottom of your tank.

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Lethargy

As mentioned earlier, if your tank contains too much CO2 then every species of fish in your tank will behave differently.

So, in case of too much CO2, some fish will become very inactive and they will stay near the bottom of the tank.

2. Drop checker turns yellow

If you’re already using drop checker in your aquarium then if the liquid in the drop checker turns yellow then it is a sign that your aquarium contains too much CO2.

For those of you who don’t know what a drop checker is, it is basically a small device or equipment that you can put in your aquarium. It contains a blue liquid. If your aquarium contains too much CO2 then the liquid will turn yellow.

This is a very reliable way to know the high CO2 levels in your aquarium.

Besides, this device is very cheap. You can check its price Amazon here

3. pH and KH ratio is out of whack

If the pH and KH ratio of your aquarium is out of whack then this shows that your aquarium has too much CO2.

Now let me explain this one.

Basically, you can know the CO2 levels in your aquarium by measuring the pH and KH of your aquarium water.

Once you know the pH and KH of the water of your aquarium then you can refer to the table below.

(source)

If the values of your pH and KH come in the red zone then your aquarium contains too much CO2.

If the values of pH and KH are in the green zone then your aquarium contains moderate CO2 which is ideal for the fish in your aquarium.

If the pH and KH values of your aquarium water are in the blue zone then it suggests that your tank contains low CO2.

However, this method is not very reliable for measuring CO2 levels in your aquarium.

This is because it considers pH to measure the co2 in your aquarium.

Though CO2 does affect the pH of the water of your aquarium, there can be other acidifying acids like nitric acid and humic acids in your aquarium that can also affect the pH of the water of your aquarium.

Another thing is as it relies on the pH and KH values of the water of your aquarium if the values that you’ve measured with the test kit are not accurate. Then basically you are getting inaccurate information which leads to an inaccurate conclusion about the co2 levels in your aquarium.

14 Best Fast Growing Aquarium Plants (without CO2)

2 Ways to reduce CO2 in your aquarium

1. Adjust needle valve

If you’re already using a CO2 injection system in your aquarium. And your aquarium has more than 30 PPM CO2 then you can easily reduce the CO2 by adjusting the needle valve.

2. Aerating the tank

If your aquarium has a lot of CO2 i.e. more than 30 PPM then this can be a problem for the fish in your tank.

Because if your aquarium has too much CO2, the fish in your aquarium will suffocate. Because too much CO2 reduces fish’s ability to inhale oxygen.

So, in this case, aerating the tank will help to oxygenate the tank.

To aerate your aquarium, you can put a an air pump in the corner of your aquarium.

There are a lot of air pumps available in the market. We recommend Tetra Whisper Air Pump because it s very reliable. You can check its price at Amazon here.

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FAQ

Can you have too much CO2 in your aquarium?

Yes, if your aquarium contains more than 30 PPM CO2 then it is usually considered as too much CO2.

Because CO2 more than 30 PPM can be toxic for the fish in your aquarium. This is because the fish can struggle to get oxygen if case your tank contains too much CO2.

Can too much CO2 kill fish?

Yes, if your aquarium has too much CO2 i.e. CO2 levels more than 30 PPM then it is toxic for your fish.

This is because if your aquarium has too much CO2 it reduces the ability of fish to take oxygen in and your fish will struggle to get oxygen.

This will suffocate the fish and it can even cause death.

How much CO2 do aquarium plants need?

Usually, CO2 about 30 PPM is considered optimum for plants.

However, the CO2 requirements for every plant are different.

Easy aquarium plants can do well in low CO2 that is 3-5 mg for a liter.

Moderate aquarium plants can do well with about 10 to 15 mg CO2 per liter.

And high aquarium plants i.e. the plants that require special attention are usually very demanding and they require 15 to 30 mg CO2 per liter.

Do Aquarium Plants Need CO2? (Can you keep them without co2)

Conclusion

Overall, you can know if your aquarium has too much CO2 from the behavior of your fish. Or from drop checker or by measuring the pH and KH of your aquarium water.

I hope you found this article helpful.

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