Importance of CO2 in Aquariums

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Carbon Dioxide, or CO 2, is a naturally occurring chemical compound that is very abundant in nature.   While it is very abundant in nature, it is not so common in a closed system like an aquarium.  CO 2 is used by plants, along with light, to photosynthesize, thereby allowing for good health and lush growth.  Plants in an aquarium system are very important not only for how nice they look, but they also help to provide oxygen and additional food which your fish and other animals will surely thrive on.  In short, a good level of CO 2 will help keep a much more stable biology for all the living things in your aquarium.
In the aquarium, CO 2 is produced as waste breaks down, through biological filtration, or through animal respiration.  It’s even produced in small amounts by the plants themselves.  But it’s not going to be enough to maintain or promote health in aquarium plants.  Any many cases, the plants in the aquarium will exhaust the CO 2 supply in a very short time.  This has the additional adverse effect of dropping the water’s buffering capacity (the ability for the water to maintain its pH level). 
There are products available that can help you maintain a good constant balance of CO 2 saturated in your aquarium water.  Whichever system you choose, it is very important to test your CO 2 and pH levels often.  If your pH level drops too low, or goes too high, it can have disastrous effects on how all the chemical reactions in your aquarium remain stable and react with each other.              
There are 3 types of mechanical systems available to help:
  • Manual injection:  Normally a canister using fermenting yeast to produce CO2, and a power head for injection into the water.  This is a perfectly fine solution for smaller aquariums, but will prove inadequate for larger mediums.
  • Semi-automatic injection:  Essentially the same function as a manual system except that it uses a solenoid driven valve to regulate the flow of CO2 into the water.  This type of system is normally timed along with the lighting for the aquarium.  Plants don’t photosynthesize when it’s dark, therefore they require no CO2.  This helps to keep the level stable.  This is most suitable for medium sized aquariums.
  • Fully automatic:  This is the most advanced use of a CO2 injection system.  It combines the injector with the timer (either on its own or in-line with the timer used for your lights), plus gauges that constantly show the current levels of CO2 and pH in your aquarium.  This sort of system is most widely used in very large aquarium systems with a large amount of plant life.
All of these products are available online at 
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