Aquarium Tools

Free aquarium and fishkeeping calculators that run entirely in your browser — tank volume and weight, fish stocking, heater wattage, filter turnover, substrate depth, CO₂ dosing, planted-tank fertilisers, water-change dilution, salt mix, salinity conversion and safe glass thickness. For freshwater, planted and reef tanks. Nothing uploaded.

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Aquarium Volume Calculator

Find a fish tank's water volume in liters, US and imperial gallons from its shape and dimensions, with a fill allowance for substrate and decor.

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Aquarium Filled Weight Calculator

Estimate a stocked fish tank's total filled weight — glass, water, substrate and rock — and the floor load, to check stand and floor limits before setup.

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Fish Stocking Calculator

Check safe fish stocking with both the inch-per-gallon rule and the surface-area method, flagging over- or under-stocking for freshwater or marine tanks.

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Aquarium Heater Wattage Calculator

Find the heater wattage needed to hold your target tank temperature above the coldest room temperature, with a recommended standard heater size.

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Filter Turnover (GPH) Calculator

Find the filter flow rate (GPH or LPH) needed for a target tank turnover, and check whether a rated filter is adequate after real-world media derating.

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Aquarium Substrate Calculator

Calculate the weight of gravel, sand or aquasoil needed for a chosen substrate depth across your tank footprint, plus how many bags to buy.

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Planted Tank CO2 / KH-pH Calculator

Estimate dissolved CO2 in a planted aquarium from KH and pH, and find the pH drop needed to reach a target CO2 level.

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Planted Tank Fertilizer Dosing (EI/PPS)

Convert a target N-P-K or micro ppm into grams or teaspoons of dry aquarium fertilizer salt per dose for your tank volume (EI/PPS-Pro).

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Water Change Calculator

Find the water-change volume, number of changes, or resulting value needed to move nitrate, TDS or salinity toward a target concentration.

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Marine Salt Mix Calculator

Calculate how much reef or marine salt to add to RO/DI water to reach a target salinity or specific gravity, plus adjustment dosing.

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Salinity & Specific Gravity Converter

Convert between salinity (ppt), specific gravity, and conductivity for marine tanks, with hydrometer temperature correction to 25 °C.

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Aquarium Glass Thickness Calculator

Estimate the minimum safe glass pane thickness for a DIY aquarium from water height and pane size using flat-plate bending stress.

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