If the power goes out you have 3 main issues;

1. Lack of heat for your fish
2. No filtration meaning ammonia may become an issue.
3. No surface movement may lead to oxygen depletion.

If you’ve got notice there is a risk of power cuts, you can get a battery-powered or USB powered air pump. If you get a USB one then you will need a power source, some batteries for drills and other power tools can be fitted with an adaptor to use USB devices. Make sure your power source is charged. Heaters are more problematic, but a camping stove or heater is your best option to keep the room warm and safe for you, as well as the fish.

But if you don’t have any warning then you will need to deal with this right now. Point 1, your safety is more important so don’t do anything that will put you at risk. Running a gas heater in a sealed house will use up oxygen and increase carbon dioxide.

Firstly stop your tank losing heat.

Drop a duvet, rug, or blanket over the tank, or a load of towels is equally useful. Avoid lifting them off to check the fish if you can. Most fish can take a significant drop in temperature. Once power is returned don’t allow the tank to warm up too fast. If all the fish are swimming and upright allow it to warm up by about a degree an hour.

If the power is off long enough that the fish are starting to struggle and you can heat water then this is likely to be the best option. Add small amounts of warm, not boiling water in regular intervals or put warm water in plastic bottles and put these in your tank. Let your electricity supplier (not the one you pay the bill to, dial 105 to find out who is your supplier if your power is out) know you have animals and that they are struggling.

Keep your filter safe.

You will need your filter working once the power comes back on. The thing that will kill the bacteria and archaea is a lack of oxygen. Take the biomedia out of the filter if you can and pop it in a pillowcase or similar and put it in the middle of the tank. If you don’t clean your filter very often then shut it off and take it out of the tank and put it in a bucket of tank water.

Lack of oxygen

This is the most difficult one. There isn’t a lot you can do. If the fish start gasping at the surface you can try picking up water in a jug and pouring it back in. At this point it’s best to hope you’re not overstocked and that the power will be back on soon enough.

Most power outages are short, but make sure to let your energy company know you have animals in distress. If it’s likely to be off for more than 12 hours start thinking about moving the fish to someone who has power. Your local fish shop may be willing to help, and if you still have mobile power get online and see who has power and is relatively close. Take your fish in a bucket, take your filter, heater and if you have it an air pump, as well as dechlorinator. At the other end, use a plastic tub or similar to set up a temporary tank. Do not put yourself in danger to move your fish.

For more info on what to do in a power cut check out the following link.

https://www.nationalgrid.com/uk/electricity-transmission/contact-us/power-cuts