FOR SALTWATER & REEF KEEPERS

Know your reef.
Not just log it.

Test your water, log it in seconds, and ReefLog tells you what to do — specific, safe advice from your own readings, not just another chart.

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iPhone · iOS 17+ · Everything works on-device

It reads your tank like an expert

ReefLog combines your live readings, their trends, and reef-chemistry facts to reason across parameters — the way a seasoned reefer would.

⚠ Act

Your alkalinity won't hold — magnesium is why

Alkalinity is low at 6.4 dKH, and magnesium is only 1180 ppm — under the 1300 it needs. Without enough magnesium, calcium carbonate keeps precipitating out, so alkalinity falls no matter how much you dose.

Fix magnesium first: raise it to ~1300 ppm. Once it's up, alkalinity stabilizes on its own.

Everything a reef keeper needs

Fast to log, honest about the numbers, and private by design.

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Log in seconds

Alkalinity, calcium, magnesium, nitrate, phosphate, salinity, temperature and pH — each with its safe target range and a live in-range check.

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Advice that reasons

Out-of-range or drifting? ReefLog explains why and tells you exactly what to do — direction-specific, coral-safe, sourced from real husbandry.

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Dosing planner

Calibrate a supplement once to your tank and ReefLog computes the exact mL to dose — split safely across days, never guessing a product's strength.

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Trends & stability

History charts with your ideal band, a tank-stability score, and projections that warn you before a parameter leaves range.

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Maintenance reminders

Water changes, testing, filter and skimmer upkeep — scheduled and reminded, all on-device.

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Private by design

No accounts, no servers, no tracking. Your tank data never leaves your phone. Export to CSV any time.

Simple, honest pricing

The whole app is free for your tank. Pay once — only if you keep more than one.

Free — one tank, everything included
Unlock unlimited tanks with a one-time purchase. No subscription, ever.