Reef Monitor: Saltwater Log
Tank tests, trends & dosing
Only for iPhone
Free · Designed for iPhone. Not verified for macOS.
iPhone
Built by a reef keeper. Live in-range verdict as you log, test-kit timers, alk consumption rate, full CSV backup, 15 languages. Free, offline, no ads, no account.
Reef Monitor is the free, offline saltwater aquarium log for reef keepers who actually test their water.
Log a reading in seconds with wet hands, see the verdict before you save, and catch alkalinity drift before your corals do.
Free forever. No account. No ads. No tracking. Works with Salifert test kits.
QUICK LOGGING, BUILT FOR THE TEST BENCH
Large touch targets sized for wet hands.
Plus and minus steppers tuned per parameter, clamped to physically sensible bounds.
The last recorded value is pre-filled, with your target range right under it.
Built-in test timers (30-second shake, 3-minute wait) placed in the order you actually work: shake, wait, read, enter. They keep counting if your phone locks.
THE VERDICT BEFORE YOU SAVE
The value recolors live as you step past your own thresholds.
"Within target range" or "Below target range" appears before you commit.
Saves that land out of range buzz differently than healthy ones.
TRENDS THAT THINK LIKE A REEF KEEPER
Charts over 7, 30, 90 days or the entire history, with painted target zones.
Alkalinity consumption rate (dKH per day), fitted on the recent dosing regime, with direction: falling means consumption, rising means check your dosing.
Alkalinity swing alert when KH moves more than 1 dKH within 24 hours.
NO3:PO4 ratio and Ca/Alk/Mg ionic balance checks that only pair fresh readings, and every alert tells you what to do next, not just what is wrong.
Compare parameters in a stacked view, each with its own scale and target band.
Full history with inline edit and delete.
CORRECTIONS, CORRELATED
Dosing log: Kalkwasser, 2-part, All-for-Reef, or any custom product.
Water changes: percentage, salt brand, dilution in g/L.
Doses appear as markers on the charts they affect; water changes on every chart.
Mis-typed an entry? Delete it. Nothing is permanent by accident.
MULTI-TANK
Every aquarium in one app, switchable in one tap from any screen.
Each tank keeps its own readings, thresholds, dosing log, and water changes.
UNIT FLEXIBILITY
Temperature in °C or °F. Salinity as specific gravity or ppt.
Alkalinity in dKH, meq/L, or ppm CaCO₃. Nitrate as NO3 or NO₃-N. Phosphate in ppm or ppb.
Steppers, defaults, and thresholds adapt automatically. Comma and dot decimals both work.
WHAT YOU CAN TRACK
Up to 15 parameters.
Water chemistry: temperature, salinity, pH, alkalinity, calcium, magnesium, potassium, strontium, iodine, boron.
Nutrients: nitrate, phosphate, ammonia, nitrite, silicate.
Enable only what you test. Hide the rest.
YOUR DATA STAYS YOURS
100% local storage on your device. No cloud, no account, no sign-in.
The app does not make a single network request. Zero analytics, zero ads.
Full CSV backup: readings, doses, water changes, and thresholds in one file.
Import shows a preview and skips duplicates. Your data is never trapped.
15 LANGUAGES, ACCESSIBLE TO EVERYONE
English, French, German, Spanish, Portuguese, Italian, Dutch, Russian, Japanese, Korean, Chinese, Arabic, Hindi, Turkish, Polish. Auto-detected, no setup.
Full VoiceOver support, and status is never shown by color alone.
WHO THIS IS FOR
Nano reefers tracking 4 parameters. SPS keepers tracking 10.
Mixed-reef hobbyists who run their test kits every Sunday.
Anyone who has ever forgotten what their alkalinity was three weeks ago.
PRICING
Free. Forever. No in-app purchases, no subscription, no paywalls, no ads.
PRIVACY
https://nicolasbertrand-qara.github.io/reef-monitor/privacy.html
Short version: nothing leaves your device.
FEEDBACK
Found a bug? Want a feature? Email the developer: delegue.grs@gmail.com
Built by one reef keeper for the reef community. Every email gets read.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
What's new in version 1.5.0:
Your save now tells you the verdict.
• The value recolors live as you pass your thresholds, and "Within target range" (or not) appears before you save. Out-of-range saves buzz differently.
• Built-in test timers moved above the value, matching the real sequence: shake, wait, read, enter. They keep counting if the phone locks.
• New alkalinity swing alert: a move of more than 1 dKH within 24 hours raises a banner.
• Consumption rate now has a direction: rising alkalinity says "check dosing".
• Full backup: CSV export now includes doses, water changes, and thresholds. Import shows a preview and skips duplicates.
• Doses and water changes can now be deleted.
• Comma decimals ("8,2") save correctly in every language.
• Full VoiceOver support, larger touch targets, higher-contrast text.
The developer, Nicolas Bertrand, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Nicolas Bertrand
- Size
- 28.7 MB
- Category
- Utilities
- Compatibility
Requires iOS 15.1 or later.
- iPhone
Requires iOS 15.1 or later. - iPod touch
Requires iOS 15.1 or later. - Mac
Requires macOS 12.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- Copyright
- © 2026 Nicolas Bertrand