Shoal: Aquarium & Fish Care

Reads your own water tests and tells you where the nitrogen cycle actually is, what to do next, and why it stalled. Works offline, no account needed.

Shoal is the field journal for your aquarium. It takes the readings you already write on a scrap of paper and turns them into answers: where your cycle is, what your water is about to do, and whether the fish you are about to buy will work.

READINGS THAT MEAN SOMETHING

Log a test in seconds by tapping the colour you see in the tube instead of typing a number. Every value is judged against your tank type and your actual stock — a nitrate of 30 ppm is unremarkable in a community tank and a real problem on a reef, and Shoal knows the difference.

Tank Pulse turns your whole history into one number, then shows you exactly which points were taken off and why.

CYCLE COACH

The question every new keeper asks — "is my tank cycled?" — finally has a real answer. Shoal reads your ammonia, nitrite and nitrate history and tells you which stage you are in, what to do next, and roughly how long is left.

It also catches the reasons cycles stall: a pH that has dropped below 6.5, a carbonate hardness heading for zero, ammonia dosed too high, water that is simply too cold. Those four things account for most of the "my cycle has been stuck for six weeks" posts on every forum.

STOCKING THAT ARGUES BACK

Add what lives in your tank and Shoal works out the bioload against your real water volume and your filter's turnover — then checks group minimums, adult size against your tank's footprint, temperament, fin-nipping, predation and which animals eat shrimp, snails or plants.

Every conflict comes with the reason and the fix, not just a red cross. The comfort window shows the single temperature, pH and hardness range that suits every animal you keep — and tells you plainly when no such range exists.

FISH HEALTH, WITHOUT A CONNECTION

A curated library of fish diseases, algae types and plant deficiencies, with a symptom matcher that works offline. It knows the differences that matter — white spot wants the temperature raised, columnaris wants it lowered, and confusing the two is how people lose a whole tank.

FIFTEEN CALCULATORS

Real tank volume after substrate and hardscape. Water change percentage to hit a target. Dosing from any label. CO2 from pH and KH. Remineralising RO water. Raising KH. Salt mix and lowering salinity. EI fertiliser. Heater and filter sizing. Substrate weight. Evaporation. Feeding. Unit conversion.

Plus a guided drip acclimation timer that taps your wrist at every step.

YOUR DATA IS YOURS

Shoal works completely without an account — everything lives on your device and exports as JSON or CSV in one tap. Sign in only if you want an encrypted backup and sync across your devices, with email, Google or Apple. You can delete your account, and everything stored with it, from inside the app.

No ads. No analytics. No tracking.

SHOAL PRO

Shoal is free and genuinely useful on one tank. Pro adds unlimited tanks, your full reading history and trends, the complete compatibility engine, every calculator, cloud sync and the AI Tank Vet — photo diagnosis for disease, algae and plant deficiency, read alongside your actual water readings.

Shoal is a record-keeping and reference tool for hobbyists. It is not veterinary advice.

SUBSCRIPTION TERMS Shoal Pro is offered as a monthly or yearly auto-renewable subscription, or as a one-time Lifetime purchase. A subscription renews automatically unless auto-renew is turned off at least 24 hours before the end of the current period. Manage or cancel it at any time in your App Store account settings.

Terms of Use (EULA): https://szymdzie.github.io/shoal/terms.html Privacy Policy: https://szymdzie.github.io/shoal/privacy.html