Aquarium Size Calculator

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The old "one inch of fish per gallon" rule is dangerously oversimplified. A 2-inch goldfish produces far more waste than a 2-inch neon tetra. What matters is bioload (waste production), swimming space needs, and territory requirements. Goldfish are the most commonly under-tanked fish — they need 10-20 gallons per fish, not the bowls they are often sold with. The most important thing in fishkeeping is the nitrogen cycle: beneficial bacteria convert toxic ammonia (from fish waste) into less harmful nitrate. This cycle takes 4-6 weeks to establish in a new tank. Adding fish before the cycle completes is the number one cause of fish death. Test water parameters weekly with a liquid test kit (not strips). Bigger tanks are more forgiving of mistakes because the larger water volume dilutes toxins.