Aquarium measurement

Aquarium unit converter

Convert volume, temperature, length, pump flow, general hardness, and alkalinity without silently mixing US and imperial gallons or chemistry conventions.

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Converted value

Volume

75.70824 L

20 US gal = 75.70824 L

Convention used

US liquid gallons and UK imperial gallons are separate units. Check the source label before converting.

Six measurement groups

Convert volume, temperature, tank dimensions, pump flow, general hardness, and alkalinity in one place.

No ambiguous gallons

US liquid gallons and UK imperial gallons are labeled separately because they differ by about 20 percent.

Chemistry context included

GH and alkalinity conversions specify the CaCO₃-equivalent basis instead of presenting unlike quantities as interchangeable.

Aquarium unit conversion guide

The number is only useful when the unit convention is explicit.

Aquarium equipment, test kits, labels, and care sheets commonly mix metric and US customary measurements. The converter keeps US and imperial gallons separate and explains what GH and alkalinity units actually represent.

Aquarium volume: liters, US gallons, and imperial gallons

One US liquid gallon equals exactly 3.785411784 liters, while one UK imperial gallon equals 4.54609 liters. A 20 US gallon aquarium is about 75.708 liters, but 20 imperial gallons is about 90.922 liters.

Product names and informal posts sometimes say only “gallons.” Identify the market or check a printed liter capacity before using the number for dosing, stocking, water changes, or equipment sizing.

Aquarium temperature: Celsius and Fahrenheit

Convert Fahrenheit to Celsius by subtracting 32 and dividing by 1.8. Convert Celsius to Fahrenheit by multiplying by 1.8 and adding 32. Kelvin uses the same interval size as Celsius with a 273.15 offset.

A conversion does not choose a suitable temperature. Compare the result with the overlap required by every species in the aquarium and verify it with a separate thermometer when heater accuracy matters.

Tank dimensions and pump flow

The international inch is exactly 2.54 centimeters. Flow-rate conversion uses the same volume definition over time, so one US GPH equals 3.785411784 liters per hour.

Converting a pump box rating does not make it a delivered-flow measurement. Head height, plumbing, media, and fouling can reduce output, so use the filter-flow calculator for operating context.

What dGH and ppm as CaCO₃ mean

One German degree of general hardness is treated here as 17.848 mg/L expressed as calcium carbonate equivalent. The conversion changes the reporting unit; it does not reveal how much of the hardness comes from calcium versus magnesium.

A water utility may report hardness as mg/L or ppm as CaCO₃. In dilute fresh water those numeric mg/L and ppm values are commonly treated as equivalent for aquarium comparisons.

dKH, meq/L, and alkalinity as CaCO₃

Aquarium carbonate hardness in dKH is commonly converted using 17.848 mg/L as CaCO₃ per degree. Alkalinity expressed in meq/L converts using about 50.04345 mg/L as CaCO₃ per meq/L, making 1 meq/L about 2.804 dKH.

Alkalinity is acid-neutralizing capacity. It can include bicarbonate, carbonate, borate, hydroxide, and other contributors depending on the water, so a unit conversion alone does not determine carbonate or bicarbonate concentration.

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