Cherry shrimp are tiny, numerous, and far hardier about hunger than about change. In a long power cut, a cherry shrimp colony's real enemies are a fast temperature swing, a well-meant water change with mismatched water, and food rotting in still water — not the darkness or the quiet. Almost everything useful you can do for them involves slowing change down and then leaving the tank alone.
Do almost nothing, deliberately, in the first hours
A cherry shrimp tank with no filter and no light is not an emergency in its first hours, because the colony's combined body mass is tiny and its oxygen demand is low. Leave the lid on and the tank closed: opening it repeatedly to check loses heat and invites dust and household sprays into water that no filter is cleaning. Shrimp continue grazing the biofilm and algae on plants and glass exactly as usual, in the dark, without any help from you. Note the time the power failed and the tank's temperature then — that starting point is what later decisions get measured against.
Slow the cooling, never chase the temperature back up
Wrap the cherry shrimp tank in blankets, towels, or sleeping bags, glass included, so whatever heat the water holds leaves slowly. Gradual cooling is something cherry shrimp tolerate well — they live comfortably in unheated indoor tanks in many homes — while a sudden correction is not. Never pour in warm water, and never float containers of hot water in a shrimp tank: the local hot spot and the rapid shift can trigger failed moults, which are a common way shrimp die after a disturbance. If the room itself can be kept a little warmer with safe household heating, warming the room is gentler than warming the water directly.
Protect the water by withholding food and changes
Stop feeding the cherry shrimp entirely for the duration of the cut. A colony that grazes constantly needs no delivered food over days, and every pellet or wafer added to unfiltered water decays into ammonia that the stopped filter cannot process. Skip water changes too, unless the water was already poor when the power failed: replacement water at a different temperature or mineral content is one of the sharpest shocks a shrimp can receive, and in a still tank the existing water is at least the water the colony is acclimatised to. If plants are in the tank, leave them — they are food, shelter, and a small oxygen source in daylight.
Watch the colony, and know the real warning signs
Shrimp gathered at the surface in a tight cluster, frantic swimming from normally placid grazers, or individuals lying on their sides are signs the water itself has turned, usually from low oxygen or fouling, and those signs — not the clock — justify action. A battery air pump with a gentle airstone, if you have one, is the safest intervention because it moves oxygen in without changing the water at all. When power returns, restart equipment, then watch over the following days for moulting trouble rather than assuming the danger passed with the lights. During the cut itself, KinsLe Kinny can be asked what to check next as conditions change, keeping the colony's notes beside its profile for the next outage.