Oxygen brings life to your pond, but hot summer weather can cause problems. Hereâ€™s how to make sure thereâ€™s always enough for your livestock.
Oxygen can be affected by various factors. Temperature has a significant role, with cooler water holding more dissolved oxygen than warmer.
Barometric pressure also plays its part, with periods of very low air pressure creating O2 deficits.
Planting is also in the equation, with plants producing oxygen over the course of photosynthesis, but removing it during the night as they respire.
Algaecides reduce oxygen content as they kill off algae and create organic waste.
Rectifying a lack of oxygen is simple enough. The common error, however, is to rely on more oxygenating plants as these only have some effect.
Turning over the water is the best way to increase oxygen in your pond. This may involve installing a simple pump and fountain, or maybe something extra.
A fountain pump works to lift water from the lower levels of the pond, splashing it back down on the surface. This increases surface area and allows for more gas to exchange itself across the water membrane.
It also brings water from the bottom where it is running with less oxygen and mixing it with the oxygen-rich surface.
Problems arise as many people will turn their fountains off at night, using them only as a decorative feature during the day — but it is at night when oxygen demand is greatest. This is even more of a problem with solar-powered pumps which do not activate at this essential time.
Waterfalls are another excellent way of bringing needed movement and gas exchange. As the thin film of water runs down the slope, it absorbs oxygen which then transfers to the pond below. There are good reasons why fish congregate underneath waterfalls at times of low oxygen!
An air pump will also aerate a pond, although many people believe that the bubbles themselves provide the oxygen content. This is not the case, as the increased surface area and water movement do the work. Air pumps need to sit outside the pond, with a length of air line feeding from them and connected to an air stone or diffuser that sits in the pond — ideally at the deepest part.
Take care when purchasing an air pump, as some are not weatherproof and will short-circuit or corrode if exposed to the elements. They may need to be protected, or even run in a housing with a long length of air line connecting to the pond.
Air blowers are also available for larger ponds. These are essentially gigantic air pumps that turn over huge volumes of air. They connect to a branching network of air lines that then aerate the pond in multiple areas.
Modern air pumps and blowers can be picked up surprisingly cheaply if you shop around.
Why not take out a subscription to Practical Fishkeeping magazine? See our latest subscription offer.