Free aquarium calculators

Plan, calculate, and care for your tank — no sign-in, no extra steps.

Where to start

Check if your tank is ready to stock: GH, KH, pH, ammonia, nitrite, and nitrate for chosen species.

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Build a list of gear, tests, and meds — nothing forgotten before setup or a shop trip.

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Forecast GH, KH, nitrate, and TDS after a partial change — before you drain water.

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Estimate dissolved CO₂ from pH and KH for planted tanks.

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GH+ NILPA dose for tank volume and target general hardness.

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KH+ NILPA dose for tank volume and target carbonate hardness.

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pH+ NILPA dose to raise acidity.

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pH− NILPA dose to lower acidity.

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Log events, track water parameters, care tasks, and livestock. Your tank history in one place.

Calculators are free without sign-in. Email sign-in — for journal and water tests.