First checks before touching the filter itself
A fish sitter facing a stopped filter should start outside the tank, because many silent filters are simply unpowered. Ask them to confirm the plug is fully in, the strip switch is on, the house circuit has not tripped and any timer in the line has not cut the supply. Your written note should name which of those your model tends to do and what you want tried first. No sitter should open a canister filter or strip a motor housing on guesswork; external units especially can spill a cabinet's worth of water if a seal is broken by an unfamiliar hand.
Restarting safely without harming the media
The living heart of a filter is its media, so the sitter's restart steps must protect it above the hardware. If your filter needs priming, your note should say exactly how much tank water to pour in and where, using water dipped from the aquarium itself. Media that looks dirty stays dirty during your holiday on purpose; the sitter must never rinse sponges or ceramics under a tap, because chlorinated water and vigorous cleaning strip away the very bacteria that keep the tank safe.
After a restart, the sitter watches for steady flow, checks every joint and hose for drips for several minutes, and confirms fish behaviour is settling. A filter that restarts then stops again, rattles loudly or leaks at a seal should be switched off at the plug and reported, with the backup air pump started instead. Your backup plan should already include a battery air pump and air stone by the tank, tested before departure, and the instruction is simple: run it continuously until the filter works again or you direct otherwise. In a warm room or a heavily stocked tank, that bubbling buys the hours that matter.
Feeding pauses while the filter is down, and the sitter should understand why: uneaten and eaten food both become waste that a silent filter cannot process. Lights can stay on their timer, lids stay closed, and no water change happens unless you, having seen photos and a thermometer reading, ask for a specific amount with prepared water. Calm fish, moving surface and no new food is a stable holding pattern for a day in most home tanks.
What the sitter should report, and how fast
A stopped filter is a same-hour message, not an item for the evening roundup. Ask the sitter to send the time they found it, whether power was on, what they tried, the thermometer reading and a short video of the fish and the water surface. That set of facts lets you decide from a distance whether to guide a second attempt, call your aquatic shop, or ask a neighbour with fish experience to attend.
Agree in advance who else the sitter may contact: your named second person, the local aquatic store, or a veterinarian with fish experience if fish are gasping, lying on their sides or dying while filtration is off. The sitter describes and photographs rather than diagnoses, and adds no medicines, conditioners beyond your written note, or borrowed equipment from another household's tank, which can carry problems of its own.
Writing the fault plan before you leave
All of this works only if it was written while you were calm and at home. Leave a one-page fault sheet inside the cabinet door: plug labels, priming steps for your exact filter, air pump location, feeding pause rule and the contacts in order. Walk the sitter through it once in person, including a practice run of fitting the air stone, and stick a label on the filter plug so the wrong device is never unplugged in a hurry.
When the fault happens, clear fast communication matters as much as the spare pump. KinsLe Messenger keeps every conversation about your fish in one per-pet communications hub, so the sitter's photos, your instructions and a family member's updates stay together in a single thread.