Scientific Fish Tools

Evidence-Based Aquarium Calculators for Better Fish Care

By The Aquarium Calculators Editorial Team

Professional-grade calculators for water chemistry, stocking density, filtration, and diagnostic fish care.

Scientific Calculators
30+
Knowledge Entities
100+
Expert FAQs
250+
Most Used

Ammonia Toxicity Calculator (Free NH3)

Enter your test kit reading (TAN), pH, and temperature — get an instant SAFE or LETHAL verdict for Free Ammonia (NH3). Built for API Master Kit users, cichlid tanks, reef setups, and fish breeders.

Calculate Ammonia Toxicity (Free NH3)

Discovery strip

Most Used This Week

1 Week 1 Ammonia Toxicity Calculator (Free NH3) 2 Week 2 Nitrite Toxicity Risk Calculator 3 Week 3 Aquarium Nitrogen Cycle Tracker 4 Week 4 Is My Tank Overstocked? Instant Checker

Species-Specific Stocking Hub

We've preconfigured exact bioload coefficients for over 100 fish species. Select your fish to calculate precisely how many you can safely keep.

Calculator discovery controls

Find a calculator by problem

Tier 1

Emergency Tools

Use these calculators first when fish health or water quality becomes a concern.

Popular

Ammonia Toxicity Calculator (Free NH3)

Enter your test kit reading (TAN), pH, and temperature — get an instant SAFE or LETHAL verdict for Free Ammonia (NH3). Built for API Master Kit users, cichlid tanks, reef setups, and fish breeders.

2 min
Open
Popular

Nitrite Toxicity Risk Calculator

Nitrite poisoning — known as Brown Blood Disease — can silently suffocate your fish even in a crystal-clear, well-oxygenated tank. This calculator factors in your actual pH and water temperature to show you exactly how toxic your nitrite reading is right now, and what you need to do about it.

2 min
Open
Popular

Aquarium Nitrogen Cycle Tracker

Stop guessing if your tank is safe for fish. Input your latest ammonia, nitrite, and nitrate test results to determine exactly which phase of the nitrogen cycle your aquarium is in, what your readings mean, and what action to take right now to move forward safely.

2 min
Open
Popular

Is My Tank Overstocked? Instant Checker

Wondering if you can squeeze in one more fish? This instant checker calculates the biological load of your current stocking against your tank size and filtration, tells you if you are overstocked, understocked, or right at the limit — and explains what to actually do about it.

2 min
Open

Tier 2

Plan Your Aquarium

Before adding fish, verify compatibility, stocking, and water requirements.

Fish Compatibility Calculator

Use the Coexistence Lab to cross-reference temperaments, temperature bounds, pH ranges, and swimming depths of freshwater species before adding them to your aquarium. Prevent territorial disputes, physical injury, and chemical shock before you buy.

2 min
Open

Aquarium Tank Volume Calculator

Calculate gross and net aquarium volume, gallons, liters, displacement, and filled weight for safer dosing, stocking, filtration, and stand planning. Use internal dimensions for accuracy.

2 min
Open

Aquarium Fish Stocking Calculator

Estimate realistic fish stocking capacity using adult size, bioload, filtration, swimming space, tank maturity, plants, and maintenance habits. Suitable for community tanks, cichlids, predators, and planted aquariums.

2 min
Open

Aquarium Water Changes Calculator

Calculate safer water change percentages for nitrate reduction, emergency dilution, routine maintenance, and stable aquarium water quality. Enter your tank volume, current and target levels — get exact gallons, serial change plans, and safety warnings for sensitive species.

2 min
Open

Aquarium Medication Dosage Calculator

Enter your tank size, substrate displacement, and medication type — get an exact safe dose based on true net water volume. Includes scaleless fish half-dose warnings for copper, formalin, and malachite green treatments.

2 min
Open

Tier 3

Equipment & Running Costs

Estimate electricity, filtration, and long-term maintenance expenses.

Annual Fish Keeping Cost Calculator

Estimate the true annual cost of your aquarium by entering tank volume, heater wattage, filter and light power, heater runtime, and local electricity rate. Get a practical itemized breakdown for heating, filtration, lighting, water, and routine consumables before you set up, upgrade, or troubleshoot a tank.

2 min
Open

Aquarium Heater Wattage Calculator

Prevent underpowering or overheating your tank by calculating the ideal heater wattage based on your actual temperature delta – the difference between room temperature and target tank temperature. Get a safe wattage recommendation and learn why two smaller heaters are safer than one large one.

2 min
Open

Aquarium Filter Turnover Rate Calculator

Never buy an underpowered filter again. Calculate exactly how much flow your aquarium needs to keep water clear, ammonia zero, and fish healthy — based on your specific tank size, stocking density, and fish species.

2 min
Open

Aquarium Energy Cost & Electricity Calculator

Estimate the real electricity cost of running your aquarium by entering the wattage and daily runtime of heaters, filters, air pumps, return pumps, protein skimmers, wavemakers, and lights. Great for budgeting a first tank, comparing equipment, troubleshooting high power bills, or planning an efficient fish room.

2 min
Open

Aquarium PAR & Light Intensity Calculator

Estimate photosynthetically active radiation at the aquarium substrate using a manufacturer's PAR reading, measurement distance, target depth, and optional water-clarity adjustment.

2 min
Open

Tier 4

Specialist Calculators

Use tabs to jump into freshwater, marine, pond, or planted specialties.

"Why Is My Fish Dying?" Diagnostic Tool

Don't panic — most fish illnesses are treatable if caught early. Select the exact symptoms your fish is showing and our diagnostic engine will identify the most likely cause, whether it's Ich, Dropsy, ammonia poisoning, or a parasite — and walk you through exactly what to do right now to save them.

2 min
Open

Aquarium Quarantine Duration & Protocol Calculator

One sick fish can crash an entire display tank in days. This calculator generates a personalized quarantine timeline and prophylactic medication schedule based on where you bought your fish, what species they are, and what symptoms — if any — are already visible. Know exactly what to treat, when to treat it, and when it is genuinely safe to move your new fish into your main tank.

2 min
Open

pH Crash Recovery Calculator

Old Tank Syndrome causes catastrophic pH crashes that chemically burn fish gills — but fixing it too fast is just as deadly. This calculator generates a personalized, day-by-day buffering schedule based on your current pH, target pH, and tank volume, so you can raise the pH at a rate your fish can physiologically survive.

2 min
Open

More Calculators

Aquarium Floor Weight Calculator

Before setting up a 20, 55, 75, 125, or larger aquarium, estimate the total loaded weight of the tank, stand, water, substrate, rock, and equipment. This calculator helps you understand floor pressure, compare safer placement options, and know when a structural engineer is worth calling.

2 min
Open

Breeding Trigger Calculator

Many Amazonian and Asian fish species refuse to breed until the rainy season arrives. Enter your tank size, current temperature, target temperature drop, and cold water temperature — get the exact volume of RO water to add, the resulting TDS change, and a pre-conditioning checklist for your species.

2 min
Open

Fish Growth Rate Estimator

Most fish are sold as tiny 1-inch juveniles that look harmless in the store — but some will reach 12, 18, or even 24 inches within a year. Enter your fish's species category and current size to visualize exactly how fast it will grow, when it will outgrow your tank, and what size aquarium it will actually need as an adult.

2 min
Open

Aquarium Salt Dosing Calculator

Calculate safer aquarium salt doses for freshwater fish treatment, stress support, nitrite emergencies, quarantine tanks, and short-term parasite management. Avoid overdosing or harming salt-sensitive species.

2 min
Open

Reef Salt Mix Brand Calculator

Calculates dry reef salt mix requirements across major commercial brands by volume or weight to hit target specific gravity.

2 min
Open

Substrate Weight & Depth Calculator

Estimate substrate weight or bag count for sand, gravel, aquasoil, sloped aquascapes, planted tanks, cichlid tanks, and reef sand beds. Avoid running out mid‑setup or creating dangerous deep beds.

2 min
Open

Aquarium Layout & Inspiration Builder

Choose an aquascaping direction based on hardscape, plants, maintenance level, livestock, budget, and whether you want a low-tech or high-tech layout. Avoid random decor and build a tank that suits your fish and your routine.

2 min
Open

Turtle Tank Size Calculator

Calculate gross aquarium capacity, actual water volume based on depth, and compare it against the general 10-gallons-per-inch of shell rule of thumb for aquatic turtles.

2 min
Open

Knowledge Journey

Continue Your Aquarium Journey

After running a calculator, open matching fish guides and focused journal articles for practical next steps.

Calculator

"Why Is My Fish Dying?" Diagnostic Tool

Don't panic — most fish illnesses are treatable if caught early. Select the exact symptoms your fish is showing and our diagnostic engine will identify the most likely cause, whether it's Ich, Dropsy, ammonia poisoning, or a parasite — and walk you through exactly what to do right now to save them.

Calculator

Ammonia Toxicity Calculator (Free NH3)

Enter your test kit reading (TAN), pH, and temperature — get an instant SAFE or LETHAL verdict for Free Ammonia (NH3). Built for API Master Kit users, cichlid tanks, reef setups, and fish breeders.

Calculator

Annual Fish Keeping Cost Calculator

Estimate the true annual cost of your aquarium by entering tank volume, heater wattage, filter and light power, heater runtime, and local electricity rate. Get a practical itemized breakdown for heating, filtration, lighting, water, and routine consumables before you set up, upgrade, or troubleshoot a tank.

Fish Guide

African Butterflyfish

Complete African Butterflyfish (Pantodon buchholzi) care guide. Learn optimal tank size (30-40+ gal), water parameters (pH 6.0-7.5, 75-86°F), surface feeding, breeding simulation, and compatible tank mates.

Fish Guide

African Cichlid

Complete African Cichlid (Mbuna/Peacock/Haplochromis) care guide. Learn optimal tank size (55-75+ gal), water parameters (pH 7.8-8.6, 75-82°F), Rift Lake setup, diet, and species compatibility.

Fish Guide

African Leaf Fish

Complete African Leaf Fish (Ctenopoma acutirostre / Leopard Bushfish) care guide. Learn optimal tank size (40-55+ gal), water parameters (pH 6.5-7.5, 75-82°F), carnivorous diet, and compatible tank mates.