Every living thing needs oxygen ... this of course includes Koi and also the bacteria that we need to provide for proper biological filtration.
Aeration is vital to maintaining a healthy pond or water garden. You can accomplish proper aeration through the use of an aerator, or creating waterfalls and fountains.
Air diffusers come in a variety of styles and sizes and have a very long life. Choose the air stone size and quantity which will match the air output of your air pump. Most air stones are rated to deliver or allow a certain amount of air per minute. Usually they are rated in cubic feet of air per minute or CFM. A small air stone may only allow 0.05 cubic feet air per minute. A large size air stone might allow 0.5 CFM. If you use too small an air stone or too few, you will place excess back pressure on the air pump. You can increase the number or size of stones or use a pressure relief valve.
To convert your air pumps rating of Liters per Minute to Cubic Feet per Minute divide LPM by 28.25 to give CFM.
Example: your HAKKO 40L will deliver over 50 LPM at 58 inches water depth. 50 ÷ 28.25 = 1.77 CFM. A 1.5” x 1.5” ceramic air stone will allow 0.25 CFM, you should use at least 7 of this size air stone.
So how much air do you need?
|Pond Volume in Gallons||1000||2000||3000||4000||5000||6000||7000||8000||9000||10,000|
|Liters of air/min required to maintain
Dissolved Oxygen at Koi Safe Levels
These numbers are intended as a guideline. Your application may vary according to stocking levels. (In general terms, 40lpm per 1000 gallons is a good rule of thumb.)