Meet Tankbook — Reef-grade water chemistry, on this phone

Lifestyle

Tankbook

Reef-grade water chemistry, on this phone.

Every feature, from the first launch.

No account, no login, no cloud. Everything runs on your device and works fully offline — nothing in this post is hidden behind a wall.

What Tankbook does

Tankbook is the offline aquarium chemistry logbook for the 14.7 million US fishkeeping households. Built for the reef keeper who tests calcium, alkalinity, magnesium, nitrate, phosphate, salinity, and pH every week — and for the freshwater planted-tank owner whose parameters matter just as much.

What ships in v1:

— Ten-second entry sheet. The parameters you actually test, big number pads, swipe through. Done in under a minute, even with wet hands. — Trend charts per parameter. Swift Charts line graph for every value, last 7/30/90/365 days. Spot a slow alkalinity slide before it crashes a coral. — Multiple tanks. Reef display, freshwater planted, quarantine, frag tank. Each has its own parameters and its own history. — Test-kit reminders. Calcium every Tuesday. Alk every Friday. EventKit notification local to this device. — OCR for color cards (Vision). Snap a photo of an API test card or refractometer scale, Tankbook reads the value into the row. — PDF chemistry report. One-tap export to take to your local fish store or share with your reef-club mentor. — Equipment log. Skimmer, calcium reactor, dosing pumps — record when you last replaced media or carbon. — Livestock list. Per-tank fish + coral + invertebrate inventory with add date. — Stays on this phone. No account, no cloud, no analytics. Your tank, your data. — Free. The AquaticLog $25-a-year paywall on reminders ends here.

For the reef keeper who's tired of the AquaPlanner data-loss horror stories, the Aquarimate UI from 2012, and the AquaticLog subscription gate.

A look inside

Tap any screenshot to open the full-resolution version.

What's inside

Tank picker — Switch between reef/freshwater/quarantine tanks
Test entry — 10-sec form for the week's parameters
Trend charts — Swift Charts per parameter, 7/30/90/365 days
OCR — Snap an API card or refractometer; VisionKit reads value
PDF report — Per-tank chemistry export via share sheet

Why we built it

Reef and planted-tank keepers test water chemistry weekly but every existing iOS app is broken (AquaPlanner data-loss horror stories), dated (Aquarimate 'UI feels designed in 2012'), or paywalled (AquaticLog $25/yr just for reminders).

What makes it different

Tankbook is the only iOS aquarium logbook with multi-tank support, per-parameter trend charts in Swift Charts, VisionKit OCR for API color cards and refractometer scales, and PDFKit chemistry-report export — all offline, no account, no $25/yr Pro tier — AquaPlanner lost users' years of data on an update, Aquarimate's…

Who it's for

Hobbyists who want a tool that respects their time, their gear, and their offline life.

In one line: Reef-grade water chemistry, on this phone.

Try it

See the Tankbook app page for the full feature list, the info table, and support links.

Use Tankbook, found a bug, or have a feature request? Comments are open below — anonymous is fine.