Start with what normal looks like
An emergency brief only works if the sitter knows the baseline. Before you leave, stand at the tank together and describe your betta on an ordinary evening: where he rests, how he rises to feed, what his breathing looks like at rest, and the temperature the thermometer should show. A sitter who has seen normal can recognise abnormal; one who has only read instructions cannot, and will either panic at ordinary betta stillness or overlook a genuinely grounded fish.
Walk the equipment physically, not on paper alone. Show them the heater light, the filter's sound and flow, the lid's fit, and the light timer, and let them feed the betta once while you watch, so the portion size and the one-piece-at-a-time pace are something they have done rather than something they have read about.
Name the failures and the first move for each
Keep the emergency list short and concrete. If the temperature has drifted well away from its usual reading, the sitter should check whether the heater is plugged in and lit, swap in the spare heater you have left beside the tank if it is not, and call you. If the filter has stopped, they should restart it if it simply lost power, keep the lid closed, skip feeding, and call you rather than rinsing or replacing anything inside it.
For the fish itself: a betta found outside the tank goes straight back into tank water in a cupped, wet hand or soft container, never under a tap, and you are called at once. A betta trapped against the filter intake should have the filter switched off first so the suction releases him. A betta that cannot rise, lies on his side, or ignores food he normally takes is a call to you and to the vet whose number is on the brief, not a watch-until-tomorrow situation.
Lines the sitter must not cross
Spell out the prohibitions kindly but plainly, because a worried sitter improvises. No adding any treatment, tonic, or home remedy to the water. No large water change unless you direct it live on a call. No feeding extra because he looks hungry, and no moving him to another container of fresh water, since new water at the wrong temperature is a shock worse than most problems it is meant to solve.
Give them explicit permission to spend your money on the vet and on a replacement heater, and say so in the written brief. Sitters hesitate at exactly the moment hesitation costs most, usually over cost or over fear of overreacting, so remove both doubts before you leave: tell them you would rather get a false-alarm call than a silent wait.
Put the brief where panic can find it
Leave one copy on paper beside the tank and the same brief in digital form, with your number, a backup contact who knows fish, the vet's number and address, and the location of the spare heater, spare air supplies if you use them, the water conditioner, and the test kit. Mark the normal temperature and the feeding amount directly on the brief in the units the sitter will actually read off the equipment.
Do a five-minute rehearsal of the most likely event, a heater failure, before you go. It feels excessive until the night it happens, when a rehearsed sitter simply executes rather than deciding under stress.
A brief only helps if it reaches the sitter in the moment rather than in a drawer, and KinsLe does that through its Care Pass, handing your sitter temporary, clear access to the betta's emergency steps, contacts, and routine while you are away.