Planted Tank Obsessed
Join Date: Mar 2013
Location: Philadelphia, PA
Airstones are used to oxygenate and circulate the water in the fish tank. However if you inject co2 in your tank and have an airstone on at the same time, the airstone will gas off your co2 rending it useless. Therefore, during the day or lights on people turn off the airstone and run co2 for their plants. During lights off, the airstones are turned on and co2 off.
This is because plants, fish, and beneficial bacteria all use oxygen. plants use co2 during lights on, and when the lights are off, they use oxygen (in scientific terms, it is something called cellular respiration, if I remember correctly). Therefore, during lights off (at night) airstones are used to provide more oxygen to the fish, bb, and plants.