Why Does My Biofilter Need So Much Oxygen?
Oxygen is a life force in any backyard pond system. It is needed by aquatic pond life, pond plants and by nitrifying bacteria. Nitrifying bacteria, responsible for converting ammonia into nitrites and then into nitrates perform a major function in garden ponds. Without the biological processes they perform in breaking down ammonia you simply would not be able to keep fish and other aquatic life such as frogs, toads etc in your pond. The reason for this is because ammonia is an extremely dangerous chemical in high concentrations. If you allow ammonia levels in your pond to rise to high you will suffer from sick fish that will eventually die. They have in effect been poisoned.
Atmospheric air is approximately 21% oxygen. This oxygen is absorbed into your pond water where it is rapidly used up by pond fish, pond plants and by the beneficial nitrifying bacteria.
The amount of oxygen in your pond water fluctuates according to pond water temperature. During hot spells it becomes increasingly more difficult for your pond to absorb oxygen from the atmosphere. You have probably noticed pond fish gasping at the surface for oxygen when the weather is hot. This is the reason why.
During winter when the pond water temperature is much lower, oxygen is much more easily absorbed by your pond, particularly if it is windy and there is much more surface movement.
Oxygen Is Critical To Biofilter Performance
Strictly speaking it isn't the pond filter that needs oxygen in large quantities it is the Nitrosomonas and Nitrobacter beneficial bacteria that are responsible for breaking down ammonia into nitrates. The chemical processes involved in converting ammonia, firstly into nitrites and then into nitrates requires an enormous amount of oxygen.
Ammonia will be ever present in any garden pond that contains pond fish and aquatic plants, apart from late fall and winter when there is very little biological activity. The ammonia is excreted into the pond by Koi, goldfish etc as they eat and by decaying organic matter, such as uneaten fish food and rotting plant life on the pond floor.
The oxygen is contained in the water being pumped through the pond filter by your pond pump. If the beneficial bacteria are starved of oxygen for more than 5 hours they will die. Don't switch off your pond pump overnight, as by then it will be too late. Biological pond filters need a constant supply of oxygenated pond water 24 hours a day.
The full article can be read at http://www.garden-pond-filters.com/garden-pond-oxygen.htm, where you will find other interesting articles and product resources.
