The Trouble with Load Shedding
It is as though a new disease is taking grip of the koi world. It is cause by the sudden shortage of oxygen in ponds due to lack of circulation or supplemental air. This happens when the main power goes a-shedding especially during weekends when you are not home.
Apart for deaths reducing the population of your prized pond collection, all sorts of other symptoms may come to light and usually a few days later. This syndrome in fish can be termed Eskomosis and is directly as a result of anoxia (see definition below). This can be fatal or lead to stress conditions that may have various secondary consequences for the fish population.
The following factors all play a roll in determining how acute the actual effect of the syndrome on your pond is.
- · Length of the power failure event
- Volume of the pond
- Pond surface area relative to volume
- Total biomass of fish (number and size)
- How much and when last have they been fed prior to the event
- Turnaround of the pond
- Presence of supplemental air (venturi’s, air diffuser or air domes)
- Biological oxygen demand of the pond (BOD)
- Effectiveness of the biological filter system
- Effectiveness of removal of settlement
- Height above sea level
- Temperature of water
From the above it is obvious that each pond has its own unique set of conditions that can potentially cause fatalities. In some ponds the loss will be minimal or none, while in other ponds the deaths will be significant. Most ponds can normally tolerate being without power for an hour or so, but once you see fish gaping for air, it is imperative that you remedie the situation immediately.
Gaping is a sign of anoxic stress and they will look around for any available air pockets, even try to swallow air, next they will become lethargic, hanging listless trying to conserve there energy. Comatose behaviour is more than likely to follow due to increased carbon dioxide concentration in the blood. Low oxygen levels impaired gill function or various other internal disease conditions can give rise to this near-death state. Then permanent brain damage and death follows quickly.
What you can do:
- With a bucket “break” the surface of the water by pouring, stir and splash the water every 15 to 30 minutes while keeping a close look at the need of the fish.
- Agitate the water with a good air diffuser and adequate 12V air pump that will match the depth of your pond.
- Use whatever backup power system you have, whether generator, UPS, battery or inverter. Using an Automatic Inverter Control or UPS to make the switching over easy.
Do not use the circulation pump unless it is low wattage and you have power reserves for that. Switching the circulation pump off is not ideal. Your filter will recover after an outage quite quickly but an air diffuser (air stone) will keep you pond “running” and save the fish using very little power. The use of a low wattage air pump (50-100 Watt) on an independent resource (battery) will do the trick.
But almost all these backup scenarios require your attention to switch over in case of the need.
We find that an UPS or Automatic Inverter Controller is economical and works well when you require power for a few hours to run an air pump. Keeping your pond requirements separate from your home requirements mean that you do not come in conflict with the family’s demand. Rather let the pond use its own backup system. You can even extend the battery life further if you use a timer to switch the air pump and/or circulation say 15 minutes on 30 minutes off.
The trouble is that under prolonged Stage 2 or higher load shedding you are restricted by how much storage capacity you have in batteries and how much time you have to recharge the batteries. Somehow you never have a win-win situation without additional capacity.
So the assistance of a generator or solar panels are always needed and relying on stored power from batteries alone is futile.
In our facility we rely on air pumps that drive the air lift pumps of ten high density holding ponds and low power water pumps. We have an alarm system that both senses the power failure as well as a drop in air pressure..
Definition of anoxia:
Anoxia is a condition characterized by an absence of oxygen supply to an organism, an organ or a tissue.
Anoxia results when oxygen is not being delivered to a part of the body. If the condition does not involve total oxygen deprivation, it is often called hypoxia, although the two terms have been used interchangeably. In fish the anoxic condition can result in stress that is the driver for the proliferation of skin parasites....
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