Comparison

Reef Book vs Reef Stability

Price, ratings, monetisation and update history for both apps, side by side β€” with what reviewers say about each.

Head to head
About

Reef Book

Features
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Smart Logbook for Aquarists Record a water test in seconds, see whether each reading is in range, and follow how your aquarium changes over time. Reef Book keeps every aquarium’s history together across iPhone, iPad, and Mac. Set up each reef, planted tank, freshwater aquarium, or other aquatic system with the parameters you test, the units you use, and the ranges you want to maintain. Record Without Friction β€’ Open Quick Record from the app, a widget, or a Shortcut β€’ Type an exact value or adjust it with a precision slider β€’ Keep repeated tests as separate readings instead of losing the individual results β€’ Mark frequently tested parameters as favorites for quicker access Understand Your Results β€’ See which readings are within range and which need attention β€’ Follow changes across recent results or your complete history β€’ Use the activity heatmap to see when you tested and spot gaps β€’ Compare supported conversions directly from a logged reading β€’ Add notes and suggested tags for maintenance, dosing, livestock changes, and other events Share and Stay in Sync β€’ Invite other aquarists to view or contribute to the same logbook β€’ Create a shareable summary, preview it, and choose what to include β€’ Keep every device up to date through iCloud β€’ Schedule automatic backups and choose how many to keep β€’ Use Reef Book without creating another account Plus fun iMessage stickers!

About

Reef Stability

Features
Read full description

Reef Stability turns your own test results into the two things every reef keeper actually needs: how much to dose, and when to leave the tank alone. Log your alkalinity, calcium, magnesium and nutrients, and Reef Stability learns how fast your tank uses each one. Then it works out the daily dose to hold it steady β€” from your data, not a generic chart. When a wobble is just test-kit noise, it says so, instead of sending you chasing a number. WHAT IT DOES - Know what to change β€” a daily dose from your own tank's measured uptake - Stability first β€” it tells you when to do nothing - Every parameter on one clean screen: alkalinity, calcium, magnesium, nitrate, phosphate, salinity, temperature, pH - Trends that filter out test-kit scatter, so you see real drift - Safe by design β€” dose changes stay within reef-safe daily limits, with extra caution for SPS - Honest by design β€” sourced chemistry, and it never invents a number it can't stand behind - Your data is yours β€” full history and CSV export, free, forever - No account, no sign-up β€” your logs stay on your device FREE Log, track and export everything β€” free, with no time limit. REEF STABILITY PREMIUM Unlocks the dose recommendations, supplement forecasting and cross-parameter interpretation. Available monthly, annually, or as a one-time lifetime purchase. Stability over chasing numbers. --- Privacy Policy: https://reefstability.com/privacy Terms of Use: https://reefstability.com/terms Subscriptions are billed to your Apple ID. An auto-renewing subscription renews unless cancelled at least 24 hours before the end of the current period; manage or cancel anytime in your App Store account settings. A lifetime purchase is a one-time payment.

Screenshots

Reef Book4 screens
Reef Stability4 screens

Verdict

The call

The clearest difference is price: Reef Stability at Free against Reef Book's $5.99. Reef Stability also leads on update cadence (weekly vs every 6 months) and iOS requirement (18.0 vs 26.0). Reef Book's advantage is in-app purchases (none vs 3) and device support (3 vs 1). On ads there is nothing between them.

Scored on Price Β· Rating Β· Positive reviews Β· Number of ratings Β· Update frequency Β· Ads Β· In-app purchases Β· Monetization Β· Best chart rank Β· Devices Β· Requires iOS

CostPrice Β· In-app purchases Β· Ads Β· Monetization

Reef Stability is free to download; Reef Book costs $5.99 up front. Reef Stability sells 3 in-app purchases, starting at $6.99 per month. Reef Book asks for nothing beyond the download.

UpkeepUpdate frequency

Reef Book ships an update every 6 months, Reef Stability weekly. The most recent releases landed on October 25, 2026 and October 11, 2026 respectively.

Scorecard5 real differences Β· 1 level
Reef Book versus Reef Stability: the parameters behind the verdict, then further details
ParameterReef BookReef Stability
Price$5.99Free β€” better
Update frequencyEvery 6 monthsWeekly β€” better
AdsNoNo
In-app purchasesNo β€” betterYes
DevicesiPhone, iPad, Mac β€” betteriPhone
Requires iOS26.018.0 β€” better
Further details β€” not scored
Size166 MB9 MB
Age rating4+4+
DeveloperReefSoft LLCYUSUF AYDIN

In-app purchases

None

Reef Book

No in-app purchases

3 purchases

Reef Stability

Subscriptions2
  • Premium Monthly$6.991 Month
  • Premium Annual$39.991 Year
One-time1
  • Premium Lifetime$89.99

Questions

Is Reef Book free?
Reef Book costs $5.99, with no in-app purchases.
Is Reef Stability free?
Reef Stability is free to download, with in-app purchases available.
Do Reef Book or Reef Stability have ads?
Neither Reef Book nor Reef Stability shows ads.
Which is updated more often, Reef Book or Reef Stability?
Reef Book ships an update every 6 months, and Reef Stability weekly. Most recently, Reef Book was updated on October 25, 2026 and Reef Stability on October 11, 2026.

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