Overfeeding is the sitter problem, and it is a design problem
More fish are lost to kind holiday feeding than to almost any other absence-related cause, and it is rarely the sitter's fault. "Feed them a pinch once a day" hands a non-keeper an impossible measurement: their pinch is not your pinch, flakes and pellets look deceptively similar in volume, and a tank of fish mobbing the surface reads as hunger to anyone who does not know that fish perform hunger professionally. Uneaten food then rots in a tank nobody is testing, and the water quietly turns. Portioning the food in advance fixes the design instead of relying on the sitter's restraint: the correct amount is decided by you, at leisure, before you go.
One container per tank per day, labelled
Use whatever you have — a compartmented pill organiser, small pots, folded paper envelopes, tiny zip bags — and fill one unit per tank per day with exactly what you would feed on that day, measured the way you actually feed it. Label each with the tank and the day, because multi-tank households confuse even willing helpers, and a portion meant for the big community tank is a feast for the shrimp nano. Then the crucial second step: put the main food tubs away, out of sight, ideally out of the room. A sitter who can see the tub will eventually top up "just a little" for a fish that looks wistful; a sitter who cannot find the tub feeds the portions and nothing else.
Portion slightly lean, and say why on the note
Lean portions are deliberate. Fish tolerate a light week far better than a heavy one — a healthy adult fish misses no meals it truly needs in a short absence, while the waste from heavy feeding actively damages the water it is swimming in. So round each portion down a fraction from your normal feed, and leave fasting days in the sequence for longer trips if your fish are adults in good condition. Explain this on the written note you leave with the portions, in plain terms: the fish will act starving, that is normal and scripted, one portion a day is genuinely enough. A sitter who understands the fish are acting is a sitter who holds the line.
Cover the details a portion alone cannot
Portions handle quantity; a few written lines handle the rest. Note which tanks, if any, get something different — the bottom feeders' wafers, the frozen food for one tank on set days, thawed in tank water first. Note that lights are on timers and need nothing, that nobody should add water treatments or "a bit of tonic", and who to call if a fish dies or equipment fails, with permission to do nothing beyond the portions until you are back if the problem is not urgent. Walk the sitter through the portions once in person if you possibly can: thirty seconds of demonstration anchors the written note better than any paragraph.
When you get home, the empties are your report
The returned containers close the loop — a full set of empties means the plan ran as designed, and a leftover portion or two tells you a day was missed, which the fish will forgive and you can ask about without drama. The portion record also feeds your own notes: if the tanks came through a week of lean, measured feeding with water as clean as when you left, that is worth remembering for next time. Passing the whole arrangement to your sitter through a KinsLe Care Pass — portions, note, contacts and all — means the instructions live with the job rather than in a text message buried under holiday photos.