About FishTankCalculator.com

Why This Site Exists

Fishkeeping runs on numbers. How many gallons is your tank, really? What size heater and filter does it need? How many fish can it safely hold? How much salt, substrate, or fertilizer? Get the numbers right and the hobby is calm and rewarding. Get them wrong and you end up with stressed fish, algae, and a tank that never quite settles. Yet most of those answers are buried in forum threads, contradictory advice, and rules of thumb that fall apart for big or messy fish.

We built FishTankCalculator.com to put the math first. Our calculators turn your tank dimensions and goals into clear, equipment-ready answers in seconds, and our guides back those answers with practical, accurate explanations for freshwater, planted, and saltwater tanks alike.

What We Do

We are a calculator-first aquarium resource for keepers of every level, from a first betta tank to a mixed reef. We research products, explain the why behind every number, and lay out your options so you can decide with confidence. Everything is written with one goal: accurate, practical help without the overwhelm.

• Calculators: tank volume, filled weight, stocking, heater wattage, filtration, substrate, water changes, CO2, salt mix, and more
• Fish species: care guides with tank size, water parameters, tankmates, and common mistakes
• Gear reviews: filters, heaters, lights, test kits, skimmers, RODI, and CO2, sized to your tank
• Water and care: the nitrogen cycle, cycling a tank, pH, hardness, algae, and maintenance
• Reference charts: bookmark-worthy tables for sizes, temperatures, parameters, and conversions
• Troubleshooting: clear fixes for cloudy water, algae, ich, and the other problems every keeper hits

How We Make Money

We are transparent about this. FishTankCalculator.com earns money through the Amazon Associates program. When we recommend a product and you buy it through our link, we earn a small commission at no extra cost to you.

This keeps the calculators and guides free. We only recommend gear we believe is genuinely good for your tank and your fish, and we will never push the undersized kits or weak equipment that set new keepers up to fail.

What We Are Not

We are not veterinarians, and our calculators are planning tools, not guarantees. Every tank is different. Nothing here is a substitute for professional advice on a sick fish.

If a fish is ill, injured, or behaving abnormally, test your water first, then reach out to a knowledgeable local fish store or an aquatic veterinarian. We are here for the planning and everyday-care decisions that happen alongside that help.

Our Approach

Warm, practical, accurate, and honest. A well-planned aquarium is one of the most relaxing things you can own, and our job is to help you get the numbers and the husbandry right so you can spend more time enjoying the view and less time second-guessing yourself.