For the aquarium owner

Two tanks on the board. The display tank: 55 gallons, planted, a community of tetras and corydoras on a metal stand in the living room, an Aquaclear 70 on the back glass, a 150-watt heater, a 5-pound CO2 cylinder feeding the regulator. The quarantine tank: 10 gallons, bare-bones, a sponge filter, on the shelf in the basement. The 25% water change every Saturday, on a calendar line. The filter rinse on the 1st of each month, on its own line. The cartridge swap every 3 months on the 1st. The heater and light timer check on the 15th. The test-kit reagents every 6 months. The CO2 cylinder on a gauge line. And the quarantine hold, 28 days from the day new fish land. That is the whole list, and it lives on one due board.

You know the last water change. Saturday, October 3: vacuum down the front glass, 14 of the 55 gallons out, the ludwigia trimmed where it shaded the tetras, ferts back in with the refill. Say that once to Muse in the chat you already have open and the row is written. Every Saturday puts the next change at October 10, 2026, and the board counts the leftover days on the calendar: 5 days left as of October 5. The bucket, the siphon, the dechlorinator: Saturday.

You know the other dates too. The filter rinse went October 1, the sponges and the impeller swished in the bucket of removed tank water, never under the tap, and one month puts the next rinse on November 1, 2026, with 27 days left as of October 5. The cartridge swap is every 3 months on the 1st: swapped October 1, 2026, so the next new cartridge goes in January 1, 2027, with 88 days left. The master test kit's reagents are every 6 months: the bottle set went in April 8, 2026, so the next set comes due October 8, 2026, with 3 days left. The heater and light timer check rides the 15th of each month: checked September 15, 78 degrees holding, lights on at 2 in the afternoon and off at 10 at night, and the next check is October 15, 2026, with 10 days left.

Before the Saturday bucket comes out, ask Muse what's due on the tanks. The water change comes back two rows, one per tank, each naming October 10 and the 5 days. The filter rinse comes back with November 1 and the 27 days. The cartridge swap comes back with January 1, 2027 and the 88 days. The reagents come back with October 8 and the 3 days. The heater and timer check comes back with October 15 and the 10 days. The board subtracts on the calendar and names what is left, and no row sits in the due path. You asked in the chat you already have open. There is no day-to-day owner app to click.

The calendar lines keep their dates. The water change is every Saturday, and the board does not slide the date because the week got busy. And a Saturday missed stays missed for the week it belongs to: if October 10 comes and goes without the bucket, the line is still due on Sunday, a day late, and it does not quietly reset midweek; the week turns over and the line is on the coming Saturday, October 17, so the cadence never drifts off Saturday. And when the change finally happens on a Tuesday, the Tuesday counts as that week's change: the next one lands on Saturday, October 24, still a Saturday, not the start of a Tuesday streak. These are the cadences you told Muse, not spec-sheet promises.

The two tanks ride one roster, and one ask writes one row per tank. The water change is one job named on both tanks: log the Saturday once and the board writes a row for the display tank and a row for the quarantine tank, the display tank's 25% with the ferts, the quarantine tank's 50% with the med (bare glass, no substrate to vacuum, so the siphon takes half the tank in one pass). The small tank carries its own clock too: six corydoras from Cascade Aquatics went into quarantine on September 12, and the 28-day hold ends October 10, 2026, with 5 days left as of October 5. The board keeps that count, so a busy Saturday does not talk you into moving unquarantined fish early.

The CO2 cylinder is not a calendar row, and the board does not pretend it is one. The regulator's gauge gets read when you think of it; say the reading in the same ask and the refill line comes due the day the gauge comes in at or under 20%, not on a date somebody guessed. A 5-pound cylinder reading 14% puts the refill on the board, 6 points under the line. Log the refill at Cascade Aquatics for $12 with the fresh reading of 85% and the line clears until the gauge says so again.

The tanks get the observation habit too. When the lights come on, tell Muse what the glass surfaced, in the same breath as the date: the ramshorn count climbing, brown diatom film back on the driftwood, the heater's suction cup slipping, the filter starting to gurgle. Muse keeps each one as a note on that line, so the tank's history rides with the tank instead of on the spiral notepad by the fish food. Fold the notes into the water change. The board keeps the lines, and the habit keeps them honest between them.

The board can call ChatGPT too. Subscribe once and ChatGPT hears before the bucket is out: the water change line lands on the due board and a signed webhook names the job. An agent that speaks MCP can hear the same board.

Every row you log stays in the service log: water changes with the ferts and the med notes, filter rinses, cartridge swaps with their cost, reagent bottles, CO2 refills, and the receipts from Cascade Aquatics for the corydoras and the ludwigia. So the day you tear the 55 down, say it once: archived. Muse archives the tank and the due board drops it that day, and the history stays: two years of water-change Saturdays, what the CO2 refills cost, the hold each batch of fish served. If the tank comes back out of the basement, one ask puts it back on the board.

One line, said plainly: Maintenance Due is a personal due board and service log for your tanks. It is not a water-chemistry monitor, a fish-health diagnostic, or a veterinary record system; it tests nothing and diagnoses nothing. The board counts the calendar days you tell it and keeps the notes you give it.

The house log on /home-maintenance-checklist shows how calendar rows look. Copy the prompt on /for-your-agent and paste it into Muse. Free.