What to do with the aquarium in case of power failure? Since many power outages are usually only of shorter duration, you should not worry immediately. Only if the failure lasts several hours, there may be a need for action.
In the aquarium there are usually three electrical devices: lighting, heating and filter.

Aquarium lighting

If the light in the aquarium fails for a short or even longer time, this is basically not a problem. Both fish and plants can easily survive several hours or even days without lighting. However, it should be noted that without light, plants no longer release oxygen into the water and you therefore have to rely on more surface movement.

Heating in the aquarium during a power outage

Most animals have no problem with temperature fluctuations. For certain fish it can get too cold for a short time, but since this is not a permanent condition, it is not so problematic. However, it can lead to problems if the aquarium is located in an unheated room, because then the water cools down faster and can also drop far below room temperature, which can lead to the death of animals. To prevent this, the temperature should be kept constantly high by regularly adding hot water.

Filtering in the event of a power failure

This takes over two important tasks in an aquarium: surface movement/current and the decomposition of pollutants. In heavily stocked tanks, oxygen deficiency can quickly become a problem if there is no surface movement for an extended period of time. To get oxygen into the aquarium despite power outages, oxygen tablets or a compressed gas cylinder can be used. Additionally, plants produce oxygen when light is present, so lighting by the sun is advisable. Likewise, more fish produce more pollutants, which are broken down more slowly without a filter. Therefore, it is advisable to change a small amount of water daily and feed only little to load the water less.