Good surface agitation is clearly the key to effective gas exchange where carbon dioxide in the water is swapped out for more oxygen from the air. One of the best ways to do this is by adding at least one air source ie like an air stone  to every aquarium, no matter what other filtration you’re using. You can achieve good surface agitation using other methods like a hang-on-back filter, but it comes at the cost of having very loud splashing sounds from the falling water.

Air stones work to circulate the air around your fish tank by producing tiny bubbles filled with oxygen. These bubbles not only work to fill your fish tank with oxygen but they also work to circulate the fish tank water by lifting the different layers within the tank to the top of the aquarium.

• An Air Stone
• Is a small weighted bubbler that produces very small bubbles in the water. This simple accessory helps to gradually diffuse air into the tank and minimizes the amount of bubbling noise you’ll hear.
• Air stones circulate the air around your fish tank by producing tiny oxygen bubbles. These bubbles can fill your fish tank with oxygen and promote water circulation by within the aquarium. This is essential for preventing a stale environment and preserving water quality.
• An air stone must remain at the bottom of a fish tank, closer to the substrate. It may be a wiser choice not to bury it into the substrate. Make sure to place your air stone in places with low water movement and still water areas to help in the circulation of the region.Placing the air stone in areas with less water movement can bring more oxygen and remove possible debris stuck in the lower parts of your tank.