Reef tank water log with dosing alerts

ConsumerMobile1 weekReact NativeExpoSupabase

The idea

Reef keepers run four-figure ecosystems on spreadsheet discipline: test alkalinity, type it into Sheets, forget to dose, and watch an SPS colony bleach because a parameter drifted for five quiet days. The existing apps (Aquarimate and peers) prove people pay, but their dated UIs are a running joke in the hobby, and none of them treat drift, rather than out-of-range values, as the thing to alarm on.

The wedge is speed plus slope: five-second logging with the last value ghosted in, and trend alerts that fire while numbers still look fine (‘will leave range in 2 days’). Dosing events drawn on the same chart as parameters closes the loop the spreadsheet never could: did the new doser setting actually move alkalinity.

Who pays

Hobbyists who spent 2 to 10 thousand dollars on a tank pay 4 dollars a month or 30 a year without blinking; the subscription gates history depth, drift alerts, and chart export, which are exactly what a serious keeper wants. Distribution is community-native: Reef2Reef and r/ReefTank run weekly parameter-help threads, and the shareable trend chart, watermarked with the app name, is designed to be the image people post there.

MVP scope

  • One tank with eight parameters and editable target ranges
  • Five-second entry flow with instant in/out-of-range colouring
  • Trend charts with shaded target bands and drift-slope warnings
  • Dosing schedules with notifications and event markers on charts
  • Shareable forum-ready chart export
  • Skip for v1: multiple tanks, ICP test imports, controller integrations (Apex/Hydros), livestock tracking, social feeds
// Build prompt — paste into Cursor / Claude Code / Lovable / Bolt
Build ReefLog, a mobile app for reef aquarium keepers. Stack: React Native with Expo, Supabase (auth and Postgres), expo-notifications for local reminders, react-native-svg or Victory Native for charts.

Core flow: onboarding creates one tank (name, volume, salt mix) and sets target ranges for eight parameters: alkalinity, calcium, magnesium, nitrate, phosphate, salinity, pH, temperature; editable reef defaults pre-filled. The home screen is built for speed: today's card shows each parameter as a chip; tapping one opens a large numeric pad with the last value ghosted, so logging a test takes under five seconds. Values outside target range colour the chip amber or red immediately, and the app computes trend slope over the last four readings, warning on drift ('alkalinity falling 0.3 dKH/day, will leave range in about 2 days') even while values are still in range, since drift kills corals before absolute numbers do.

The dosing engine: per-supplement schedules (name, dose, frequency, time) firing local notifications, with tap-to-confirm logging that builds a dosing history displayed as event markers on the parameter charts, so cause and effect are visible on one screen.

Screens: today (entry chips plus due doses), trends (per-parameter chart, 30/90/all ranges, target band shaded, dosing markers), dosing (schedules and history), settings (tank, targets, units dKH/meq/L, ppm). Export any chart as a clean shareable image sized for forum posts and Reddit, watermarked with the app name.

Pricing: free for 14 days of history; subscription at 4 dollars/month or 30/year unlocks unlimited history, drift alerts, and chart export. RevenueCat for subscriptions.

// More Consumer ideas