Co2

[Ry4n7]

I'm thinking about adding co2 to my 240litre tank, I have some plants in at the minute that are doing OK with no co2 and just sand substrate but i think I'd like to upgrade a bit.

I have no idea what I would need or where to start so could I get some idea of what equipment I'd need and the rough prices please? Thanks.

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[Colin_T]

Can you post a picture of the tank and tell us what plants you have in it?

Unless you have a really heavily planted tank with only a few fish, there is no need to add carbon dioxide (CO2). There is plenty of CO2 in the tank from the fish and filter bacteria, as well as CO2 that gets into the tank from the atmosphere.

People that use CO2 normally have a tank full of plants, high intensity lighting, and they add lots of aquarium plant fertilisers.

CO2 units can be expensive or cheap. A cheap form is simply a bottle of CO2 attached to a piece of silicon airline, which goes into the tank and has a plastic airstone on the end. The CO2 very slowly bubbles out of the airstone and ends up in the water, where the plants can use it. Other units have a small container that sits in the water and is filled up with CO2. The bottom of the container is open and the tank water is in contact with the CO2, which seeps into the tank through the water it is in contact with.

More expensive units have electronic valves and pH regulators that are attached to bottles of CO2, and they turn on and off as required.

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If you use CO2 in a tank, you should make sure there is at least 150ppm of carbonate hardness (KH) in the water. The KH stops the pH dropping due to CO2 being very acidic.
If you don't have enough KH, the pH can drop overnight and kill the fish.
If you put too much CO2 in the tank, the pH can drop and kill the fish.

I personally do not like adding CO2 to tanks because there is plenty in the air and the damage to the fish from CO2 poisoning is not nice.

 

[seangee]

I agree, the term "planted tank" means something very different to "fish tank with lots of plants in it".

 

[Byron]

And I agree too. While admittedly CO2 is usually the limiting factor assuming the light intensity/spectrum is adequate, requiring added CO2 means you are basically running an underwater plant garden and not a fish tank.

If your plants are growing now, adding CO2 is not likely to improve them, because without sufficient light (increased to balance the new level you would be establishing) and increased nutrients, CO2 beyond what is now being provided is useless. Algae will benefit.