Insulation is your main heater now
A tank loses heat through its glass, its open surface and the cold room around it, and in an outage insulation beats almost everything else you can do. Wrap the outside of the tank in blankets, towels, sleeping bags or spare coats — anything dry and thick — covering the sides and back fully and the front as far as you can while still peeking at the thermometer. Keep the lid closed and cover it too, but never drape material over a light fitting that was hot when the power failed, and leave any heater's cable area clear rather than bundled into the wrapping. Insulate the room as well: shut its door, block the draught at its base, and keep the household gathered elsewhere if a fire or stove is heating one room — moving yourself is easy, moving a tank is not an option mid-crisis.
Adding heat in small, sealed doses
When you do add heat, add it gently and in containers. Float sealed bottles or a lidded container filled with warm water — warmed on a stove or from a kettle if you have a gas hob that works without power — and let each one give up its heat gradually before swapping it for a fresh one. Never pour hot water directly into the tank: the plume scalds fish that swim through it and the temperature swing stresses everyone else. A hot water bottle resting against the outside glass, inside the blanket layer, works on the same principle. Watch the thermometer between swaps; the goal is to slow the fall and hold a tolerable plateau, and tropical fish endure a slow, shallow dip far better than a sawtooth of heating and cooling.
Water movement and the stopped filter
Cold water holds oxygen well, which is the good news, but a still tank develops cold layers and leaves the filter bacteria without flow. A battery air pump keeps water circulating gently past where the heater sits, evens out the temperature and gives the bacteria something; if you have no battery pump, stir the tank slowly by hand now and then with a clean utensil. Leave the filter media wet and undisturbed — rinsing it in tap water mid-outage adds a second crisis to the first. If the outage stretches long enough that the room is heading for genuinely cold, the media can stay in the tank itself, in the water it knows.
Feeding stops and the family rota begins
Do not feed during a winter outage. A cold fish's digestion slows to a crawl, uneaten food fouls still water, and even an eaten meal produces waste a stopped filter cannot process — the fish will come to no harm missing meals they would barely digest. The work that remains is checking: thermometer, fish behaviour, bottle swaps. That is a rota, not a solo shift, especially overnight. KinsLe's Care Teams let you assign those checks as duties to family members and mark each one completed with a timestamp, so whoever is awake at three in the morning can see the last reading and the next bottle swap is covered rather than duplicated.