When a Power Cut affects the pond

Will my fish come to any harm?

If your fish are used to having moving water from a filter, fountain, or waterfall, then a pump stoppage might cause problems. This movement aerates the water and increases its oxygen content. Problems are more likely following power cuts during warm weather, when fish, pond wildlife, and filter organisms are using more oxygen from the water. Problems are less likely in winter as cold water usually contains more dissolved oxygen to start with. Fish also slow down and use less oxygen in cold weather. www.watergardensolutions.co.uk

As long as your pond is not overstocked, and any filter has been well maintained, a power cut of an hour or so in summer, or of up to a day in the depths of winter, is unlikely to cause immediate problems.

What if the power cut lasts a long time?

The oxygen levels in the water will start to drop. The fish may start mouthing at the surface of the water. Organisms inside a biological filter will stop functioning correctly. If the problem persists, fish (especially larger fish, or oxygen-sensitive fish like orfe) may start to die, and the filter organisms may die back too.

What can I do?

• Stop feeding the fish (even if they look hungry).
• The oxygen levels in the water can be increased by maximising the area of water surface exposed to the air. Remove excess/yellowed floating leaves from waterlilies and net out excess quantities of floating aquatic plants (like duckweed). Don’t attempt to disturb the debris on the pool base during a power cut, as stirring this up will only use up valuable oxygen.
• Spray in tap water. A jetted stream of tap water from a hose directed onto the pond surface will both aerate and circulate the pool water, as well as slowly changing some of the water. You should use a suitable water conditioner to counteract the damaging effects of chlorine in the tap water (especially if you have changed more than 5% of the pond volume).
• If you have an external filter with a drain valve, drain some water from the filter base to waste, to flush out the worst of the debris. copyright www.watergardensolutions.co.uk

Planned power cuts

Ponds and filters that are well maintained will have fewer problems in the event of a power cut. If a power cut is forecast in the future, carry out routine filter maintenance a few days beforehand. By routinely removing excess wastes and debris from the pond and filter, there will be less waste to use up the oxygen in the water.

When the power restarts

• Ideally, flush stagnant water from any filter system to waste before the power restarts, gently rinsing any dirty filter media in the old pond water before draining.
• Check any non-latching RCD/trip-switches that need to be manually turned back on when the power resumes.
• If the power has been off for some time, the biological filter organisms could take four to six weeks to recover.
• Feed fish very lightly during this six week period and do not add any new fish stocks.