For manual-testing reefers

Reef chemistry,
done right.

The only reef calculator that shows your correction dose and your daily maintenance dose on one screen. No spreadsheets, no guesswork — just the right amount, today and every day.

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Free forever for the basics. No account required.

Alkalinity

10.9g NaHCO₃

CalciumSplit 2 days

40.2g CaCl₂

Magnesium

151.8g MgCl₂·6H₂O

Daily maintenance1.9 g/day

Why this matters

Most calculators tell you one number.
That's how corals die.

You have two dosing problems, not one. The correction dose brings your tank to target today. The maintenance dose replaces what your reef consumes every day. Mix them up and you either crash your chemistry or let it drift. ReefWise separates them — safely, clearly, in the units you actually measure.

Big-three coverage

Alkalinity, calcium, and magnesium — with support for NaHCO₃, Na₂CO₃, CaCl₂, MgCl₂, and brand-name two-parts from BRS, ESV, Red Sea, Seachem, and more.

Safe-dose guardrails

Exceed the daily max on calcium? ReefWise splits the dose across days automatically. Never dump 50+ ppm of Ca in one hit again.

Net water volume

Subtracts rock and sand displacement from your gross tank volume so every calculation is based on the water that actually exists.

The calculator is free forever.

Go Pro to track parameter trends over time, infer your tank's actual consumption rate, and get alerts before chemistry drifts out of range.

See Pro plans Try the calculator

Reef chemistry,done right.