Around the Clock Aeration
Oxygen is the single most important element for life in your pond or lake.
It is imperative that you run your air pump 24 hours a day 7 days a week to build up the oxygen level to the maximum your pond can hold and then maintain it at maximum level.
Atmospheric oxygen is 21%. However, water cannot hold very much oxygen at all. Pond oxygen levels near 6 to 8 ppm (parts per million) are necessary for optimal fish and pond health. This is the equivalent of only 0.0008% oxygen. Water has a saturation point for oxygen. For example at 72 degrees and sea level freshwater can only hold a maximum of 8.7 ppm. This is the saturation point. No matter how much you aerate you cannot squeeze in any more oxygen. Luckily, your pond can function well with only 70% to 80% of saturation. It is not usually economical to try and reach 100% saturation. Needless to say maintaining oxygen levels in your pond should be your number one priority. Aquatic life including fish, plants, algae, small organisms and bacteria all consume oxygen in the pond. Every pond has an “oxygen demand” depending on the load of living and decomposing organisms in the pond. A dirty pond will have a higher oxygen demand than a clean pond due to the bacterial consumption of oxygen during the decomposition process. Bacteria can actually consume more oxygen per weight than fish can. Although algae makes oxygen during the day through photosynthesis the algae will consume oxygen during the night time through the process of respiration. Often, the night hours to early morning will have the lowest oxygen levels due to the algae in combination with all other oxygen consumers. This is why it is so important to aerate your pond 24 hours a day. It takes time to build up the oxygen level to keep up with the oxygen demand and once you get the pond close to 80% saturation you need to maintain it there. An Oxygen Meter is the only real way to know what the true oxygen level in your pond really is. A good quality Oxygen Meter can be very expensive.
Ponds aerate in two ways.
1) Air bubbles dissolve oxygen directly to the surrounding water. The smaller the bubble the better the dissolution. However, small bubble diffusers typically clog up quickly and require more frequent service or cleaning. A small bubble diffuser will put excess back pressure on your air pump.
2) Surface turbulence. Such as is created by waterfall or a rising column of air bubbles bursting at the surface of the pond. A rising column of medium size bubbles lifts water from the floor of the pond to the surface bursting and creating surface turbulence which expands out in all directions. The pond breathes through the surface air / water interface. Oxygen enters the pond from the atmosphere and carbon dioxide is expelled from the water. The more turbulent the surface agitation is the better the process works. This method only requires a medium size bubble which means a diffuser that will clog less frequently and put less back pressure on the air pump. Your air pump will run longer between service intervals. Our Matala rubber membrane air discs and air hose diffusers produce a medium size bubble and do not add back pressure to the air pump.
In the summer the warm water holds less oxygen but the activity level of the fish and other organisms increases and so does there oxygen demand. Place your air diffuser in the middle of the pond at the deepest point for the most efficient air lift and surface turbulence. In Japan, the koi breeders say that the best aeration for the pond is when you have so much surface turbulence that you cannot even see the fish. Of course this is not what most hobbyists want to do but consider putting the air pump on a switch or a timer so that you may view your koi during feeding times or weekends. The rest of the day just bubble like crazy. Your fish and pond will be cleaner and healthier. Alternatively, place your diffuser in a corner or along a back wall where it will not interfere with your viewing enjoyment of the fish. Do consider how the placement of your air diffuser will affect the performance of your skimmers. Improper placement can push debris away from your skimmers. Use the surface movement created by the bubbles to compliment your skimmer suction.
In the winter time, in very cold climates, your pond may freeze over with ice. The ice will block the air / water surface interface and suffocate your pond. The water surface is the lungs of your pond. Place your air diffuser just 12 inches below the surface of the pond on a support of blocks or stones. The bubbles will keep an air hole open so the pond can still breathe. Do not put the diffuser on the bottom of the pond in the winter if water temperatures go below 45 degrees. A deep diffuser will circulate the entire pond top to bottom and will bring cold water to the bottom of the pond. If your diffuser is near the surface then the bottom of the pond will be more calm and actually stay a few degrees warmer so the fish can just hibernate without freezing.