Aquarium Calculators
Free aquarium calculators for tank volume, stocking levels, CO2 injection, and water change schedules.
Tools for freshwater and saltwater aquarists.
Volume, filtration, dosing, lighting and CO2 for freshwater and reef tanks. 14 calculators.
Tank volume is the number everything else depends on, and almost nobody has the right one. A tank sold as 200 litres holds meaningfully less once substrate, rock and hardscape go in, and the water level sits below the rim. Real volume is commonly 10 to 20% under the label. Every dose you calculate from the label figure is therefore overdosed by that margin, which is why medication and fertiliser problems cluster in heavily aquascaped tanks.
Filter turnover is worth understanding before buying, because manufacturer flow ratings are measured with no media and no head height. Loaded with media and lifting water a reasonable distance, real flow is often 30 to 50% below the box figure. The usual targets, around 4x tank volume per hour for a community tank and 10x or more for a reef, should be applied to real flow rather than rated flow.
Dosing pages take actual water volume and ask for the product’s stated concentration rather than assuming a brand, since the same additive name covers very different strengths between manufacturers.
Aquarium Medication Dosing Calculator
Calculate exact medication or supplement doses for your aquarium. Enter tank volume and dose rate per gallon to get the precise treatment amount.
Aquarium Filter Turnover Rate Calculator
Calculate aquarium filter turnover by tank volume and filter GPH. Get target turnover rates for community, planted, cichlid, and reef tanks for healthy water.
Planted Aquarium CO2 Bubble Rate Calculator
Calculate CO2 bubbles per second for planted tanks by tank size and lighting. Get a target BPS range for low, medium, and high-light planted aquaria.
Protein Skimmer Size Calculator
Size a protein skimmer for your saltwater aquarium from tank volume, bioload, and feeding level. Returns the rated tank volume and air draw to look for.
Saltwater Aquarium Salt Mix Calculator
Calculate marine salt mix in grams by aquarium volume and target salinity. Returns amounts for new setups and water change top-offs at 1.025 specific gravity.
Aquarium CO2 Injection Rate Calculator
Calculate the ideal CO2 injection rate for your planted aquarium from tank volume, plant density, and lighting. Returns bubble count per second and ppm target.
Aquarium Fish Compatibility Checker
Check aquarium fish compatibility from temperament scores and pH and temperature overlap. Returns a 0-100 community suitability rating with penalties shown.
Aquarium Lighting PAR Calculator
Calculate the PAR (Photosynthetically Active Radiation) your aquarium light delivers at substrate level based on fixture specs and tank depth.
Aquarium Plant Fertilizer Dosing Calculator
Calculate KNO3 and KH2PO4 grams per dose and trace mL per week for your planted aquarium from tank volume, plant density, lighting, and CO2 (EI method).
Aquarium Substrate Depth Calculator
Calculate aquarium substrate volume from tank dimensions and desired bed depth in inches or cm. Returns the amount needed in liters, kilograms, and pounds.
Quarantine Tank Size Calculator
Calculate quarantine tank size in gallons from fish size and count. Returns minimum volume, water change schedule, and equipment for safe fish isolation.
Aquarium Heater Size Calculator
Calculate the correct wattage aquarium heater for your tank size and room temperature. Avoid underpowered heaters that can't maintain fish health.
Aquarium Tank Volume Calculator
Calculate the actual water volume of your aquarium in gallons and liters, accounting for substrate, rocks, and equipment displacement.
Aquarium Water Change Schedule Calculator
Calculate gallons per water change plus monthly and yearly totals from tank volume, change percentage, and interval. Includes a schedule guide.