RO / Tap Water Mixing Calculator
Work out how much reverse-osmosis, rain or distilled water to blend with hard tap water to hit a target GH, for shrimp, tetras, apistos and other soft-water fish. Ratio and litres of each.
Aquarium calculators
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Planted Tank Fertiliser (EI) Dosing Calculator
Work out how many grams of dry salts (KNO3, KH2PO4, K2SO4, CSM+B traces) to dose your planted aquarium to hit target N, P, K and Fe, with EI and lean presets.
Aquarium Water Change Calculator
Work out how big a water change you need to bring nitrate or TDS from its current level down to a target, allowing for what your tap water already contains.
Aquarium Volume Calculator
Work out your aquarium's volume in litres, US gallons and UK gallons from its dimensions, for rectangle, cube, cylinder, hexagon, bowfront and corner tanks.
Aquarium Substrate Calculator
Work out how much sand, gravel or aquasoil you need for your aquarium, in litres and kilograms, from the tank footprint and the depth you want.
Aquarium Stocking Calculator & Fish Stocking Calculator
A free freshwater aquarium stocking calculator based on metabolic fish weight and filtration, not the inaccurate inch-per-gallon rule. Checks stocking level, group sizes, tank size and water-hardness suitability.
Aquarium Running Cost Calculator
Estimate what your aquarium costs to run: heater, filter and lighting electricity per day, month and year, from their wattage and your electricity price.
Aquarium Remineralisation Calculator (GH / KH)
Work out how much gypsum, Epsom salt and baking soda to add to RO or soft water to hit a target GH and KH, with a chosen calcium-to-magnesium ratio. Cheap DIY remineralisation.
Aquarium Heater Wattage Calculator
Work out the right aquarium heater wattage for your tank from its volume and how far above room temperature you need to hold it.
Aquarium CO2 Calculator (pH / KH)
Work out dissolved CO2 in your planted aquarium from pH and KH, with a safe-range guide, plus a rough planted-tank lighting estimate.
Aquarium Calculators
Free freshwater aquarium calculators: tank volume, fish stocking, heater wattage, substrate, CO2, fertiliser (EI) dosing, remineralisation, water changes, fishless-cycle ammonia and running cost.
Aquarium Ammonia Calculator: Fishless Cycle Dosing
Work out how much household ammonia to add to hit a target ammonia level for a fishless cycle, from your tank volume and the strength of the solution.