The tank at a glance: stock, size and who matters
Open with the facts a helper needs before touching anything: the tank's size, a list of every animal in it with rough counts, and anything with special sensitivity, such as shrimp that cannot tolerate big water swings or a bottom dweller that hides so well it gets counted as missing. Then list people, in the order they should be called: you, a backup household member or neighbour who has a key, the fish shop you actually use, and a vet who will advise on fish if you have one. Emergency notes fail when they assume the reader knows your household, so write them for the neighbour who has only ever waved at the tank through the door.
Equipment: which plug does what, and where the spares live
Label every plug and write the list down: heater, filter, lights, air pump, and anything on a timer. A helper facing a silent tank at midnight should be able to tell at a glance whether the filter has stopped or a timer has simply switched the lights off. Note where the practical supplies are stored — buckets, a siphon, towels, water conditioner, the spare heater, a battery air pump if you own one — and where the test kit lives with its most recent readings written beside it. Say plainly what can be switched off safely and what must never be unplugged, because in a leak the instinct to pull every plug can kill the filter bacteria the tank depends on once the water is back.
One card each for the three emergencies that actually happen
Give each scenario its own short sequence rather than one long essay. For a power cut: keep the lid closed, wrap the tank if the room is cold, stop feeding, and note who to call if the outage stretches on. For a heater failure: how to read the thermometer, what a falling reading means for this tank's stock, and when to fit the spare heater rather than wait. For a leak: which towels and buckets to grab, moving electrics out of the wet zone first, and the largest container the fish can wait in if the tank has to be drained. Short cards get followed under stress; essays get skimmed and abandoned.
Feeding rules and the 'never do this' list
Overfeeding by a kind helper is the commonest aquarium emergency of all, so state the amount, the frequency, and the rule that a missed meal is always safer than a doubled one. Close with the prohibitions that protect the tank from good intentions: never empty and scrub the whole tank, never rinse filter media under the tap, never add any chemical or remedy that is not written in these notes, never move the tank while it holds water. Keep the finished notes in two places — a copy by the tank and a copy with your backup person. KinsLe's Pet Passport holds the tank's records together as one portable packet, so its stock history, equipment list and emergency cards travel as a single set instead of scattering across drawers and phone notes.