Aquarium & Fish Calculators
All-in-one aquarium calculators: tank volume, gravel/substrate, heater, filter, stocking. Gallons, liters and UK gallons.
- Aquarium Volume CalculatorAll-in-one aquarium calculator: volume in gallons, liters & UK gallons, water weight, recommended heater wattage, filter GPH and substrate.tankOpen
- Aquarium Gravel CalculatorCalculate exactly how much gravel or sand your aquarium needs by tank size and depth. Multi-substrate (gravel, sand, planted).tankOpen
- Aquarium Stocking CalculatorCheck if your aquarium is overstocked using the AqAdvisor-style bioload model with surface-area and filtration factors.tankOpen
- Aquarium Heater CalculatorCalculate the right heater wattage for your aquarium based on tank size, target temperature and room temperature differential.equipmentOpen
- Aquarium Water Change CalculatorCalculate how many gallons of water to remove for a 10/25/50 % water change. Nitrate dilution calculator included.maintenanceOpen
- Pond Volume CalculatorCalculate pond volume in gallons and liters for rectangular, round, kidney-shaped and irregular ponds. Plus liner size and pump flow.pondOpen
- Aquarium CO2 CalculatorCalculate bubble rate (bps) and CO2 ppm for planted aquariums. Target 30 ppm for lush growth without harming fish.plantedOpen
- Aquarium Salt CalculatorCalculate the exact amount of marine salt, brackish salt or aquarium tonic salt for your tank volume and target salinity (ppt or SG).saltwaterOpen
- Aquarium PAR CalculatorCalculate the required light level (watts per gallon or PAR ΞΌmol/mΒ²/s) for planted aquariums. Low light, medium, high-tech tanks.plantedOpen
- Aquarium Fertilizer CalculatorCalculate weekly dry fertilizer doses (KNO3, KH2PO4, K2SO4, micros) for planted tanks using the Estimative Index method.plantedOpen
- Goldfish Tank SizeHow big should a goldfish tank be? Correct sizing per fish: fancy goldfish (20 gal first + 10/extra), common goldfish (pond-only: 100+ gal).speciesOpen
- Betta Tank SizeWhat size tank does a betta need? Modern standard: 5 gallons minimum filtered and heated β NOT a bowl. With plants / sorority / community tank options.speciesOpen
- Nitrogen Cycle TrackerTrack your aquarium cycle day-by-day. Logs ammonia, nitrite and nitrate progression. Ammonia dose calculator for fishless cycling.setupOpen
- Koi Pond StockingHow many koi for your pond? 250-500 gallons per adult koi (24-36 inches). Depth 4+ ft for winter.pondOpen
- Axolotl TankTank size for axolotls: 20 gal single, +10 gal each. Cold water 60-68Β°F, NO gravel (impaction risk).speciesOpen
- Fish Food CalculatorHow much to feed fish? 2-minute rule: only as much as eaten in 2 minutes. Species-specific 1-2% body weight.feedingOpen
- Aquarium Cycling TimePredict days to complete the nitrogen cycle based on tank size, bacterial starter product, ammonia source and temperature. Full milestone timeline.cyclingsetupOpen
- Aquarium Carbon NeedsGrams of activated carbon for your tank by size, goal (maintenance / medication removal / tannin / odor) and water type.filtrationOpen
About aquariums in the United States
Freshwater and saltwater aquariums are a $2.8B US hobby β 12% of households keep fish. FurCalc's aquarium calculators cover sizing, stocking, water chemistry, and planted-tank fertilization from beginner goldfish bowls to reef tanks and outdoor koi ponds.
Common mistakes our calculators prevent
Under-sized tanks (the #1 cause of fish deaths) β our volume and species-specific calculators show real minimums. Overfeeding (#2 cause β ammonia spikes) β our fish-food calculator uses the 2-minute rule. Skipping the nitrogen cycle β our cycle tracker walks you through the 4-6 week fishless cycle.
Aquarium calculator FAQ
How big a tank do I need for one fish?
Depends on species. Betta: 5 gal minimum. Fancy goldfish: 20 gal. Common goldfish / koi: pond only. Use our species-specific tank size calculators.
What's the 'inch per gallon' rule β is it accurate?
No. It fails for large fish (a 12-inch Oscar produces far more waste than twelve 1-inch neons). Modern stocking uses bioload β see our Aquarium Stocking Calculator.
How accurate are these calculator results?
Our calculators implement the exact formulas used in veterinary textbooks, AAFCO/NRC nutrition standards, AAHA/AAFP life-stage guidelines, and peer-reviewed research. Results are accurate within the precision of the input data. For medical decisions (toxicity, drug dosing, diabetic insulin), always confirm with your veterinarian β calculators are educational tools, not clinical devices.