Garden pond power failure

We live our lives at the mercy of the National Grid. From the sounding of the alarm clock in the morning and our first cuppa through to a night spent in front of the TV, with another cuppa, our lifestyle and electricity are inextricably linked.

We can suddenly lose some of our home comforts during a power failure being forced to carry out emergency measures to keep warm and comfortable. Those of us who are old enough can remember the effect that regular power cuts in the mid 1970′s had upon the public’s lifestyles – candle-lit evenings and interrupted meals.

Unfortunately, as koi keepers, the consequences for our koi are likely to be a little more severe than ‘discomfort’ as the stability of their pond environment is completely dependent on an uninterrupted supply of power.

The pump is the heart of the pond and filter system, circulating the water at a rate that is sufficient to stay ahead of the accumulation of pollutants in the pond. If the power fails and the pump stops, then the speed at which problems start to develop will be dependent on the water temperature.

An uncirculating pond is likely to soon lead to gasping koi as the dissolved oxygen level drops below the minimum required. Although not evident at the same time, the bio-filter is also likely to develop problems as the bacterial efficiency declines. This is more likely to manifest itself as a problem once power returns, with the pond experiencing a mini ammonia or nitrite crisis similar to that of a maturing new pond.

If the power failure occurs at winter then it is less of a problem as the dependency on circulation for D.O. and filtration are much reduced. However, if you are heating your pond, either electrically or by gas, then your koi are likely to experience a drop in temperature. Although not life-threatening, such unstable or extreme changes in water temperature are likely to stress koi, especially once power is resumed, when the water temperature rises to its original level.

Causes of a power failure

Essentially, there are 2 likely causes of a power failure to a koi pond:

General power failure:- The supply to the house and neighbourhood is lost. In this situation, there is little that can be done to reduce the impact on the koi and filter.

Local Power Failure:- The supply of power to the house is intact but the spur of power that supplies the pond has failed. Many houses are fitted with extremely safe (and sensitive) consumer units which replace the older type fuse boxes. Individual circuits may have an earth leakage or ‘trip’ switch which will isolate the power supply at the merest hint of a faulty circuit.

Electrical circuits that leave the house for the garden, shed, or pond are more likely to experience conditions that will cause a circuit to ‘trip’. Exposure to the elements, rodents wishing to wear down their teeth or more typical problems with electrical equipment can all lead to the most sensitive of circuits to be isolated.

In such an instance, where the safety device does not allow the circuit to be reset, a process of elimination must be followed to isolate the part of the circuit that is faulty. It may be the underwater lighting, the pump, UV or electric heater (a likely candidate, especially in the winter). Once isolated, the system should be reset, and be able to run uninterrupted thereafter.

Possible solutions

If you experience a local power failure to a single circuit, then the above procedure should be sufficient. However, if the fault is untraceable, then the pump could be powered by a temporary extension line taken from a live socket from an intact circuit in the house. This should also be protected with an earth leakage circuit breaker fitted at the plug (just as you would when mowing the lawn).


A recent innovation to be released onto the market is an air pump with a substantial battery back-up. Constantly detecting whether the power is present, the second the power fails, an integral back-up battery takes over and will power the unit for up to 8 hours. This has proven to be very popular with aquatic retailers who require such a back up for all of their ponds and aquaria should the power fail.

Those with a larger budget, and who feel very protective about their koi, can invest with a dedicated alarm system. Linked to a dialler, which informs a central monitoring station, this system will call a series of telephone numbers in the event of a power failure. In your absence, this system will immediately inform you of a power cut which can allow you several more hours to solve the problem before it is too late. This system is used as standard by many fish farmers and wholesalers where a power cut could prove to be disastrous to their valuable stock.

Oxygen on tap?

If the power failure is a general one, with no access to power, then if required, and in extreme circumstances, cold tap water can be sprayed from a hose onto the surface of the pond or even into the upper layers of the water. This will dilute the build up of toxins and increase the D.O. at the same time.

Although most power cuts are unforeseen and unavoidable, there are a limited number of measures to take to prevent it from stressing the koi. However, once the power returns, be sure to carry out a water change if required and test the water for ammonia and/or nitrite over the next week or so, to determine whether the bio-filters activity has been harmed. If a nitrite reading does occur after several days, then respond accordingly by reducing feeding and carrying out a water change until the nitrite reading is zero.

Kill blanketweed and string algae.