Aquarium Stocking Calculator
Overstocking is the number one cause of fish health problems. Use this calculator to find the safe stocking limit for your aquarium based on its volume and fish size.
As an Amazon Associate and CJ Affiliate publisher we earn from qualifying purchases. Prices and availability may vary.
Aquarium Stocking Guide
What do I need to know about The Inch-Per-Gallon Rule (and Its Limits)?
The classic '1 inch of fish per gallon' rule provides a rough starting point but has significant limitations. It does not account for fish body shape (a 6-inch Oscars needs far more space than a 6-inch neon tetra school), bioload (goldfish produce far more waste than equivalent-sized tetras), swimming patterns (active schooling fish need open swimming space), or aggression. Use it as a maximum ceiling, not a target to aim for.
What should I know about Bioload and Filtration?
Filtration is as important as tank volume. The nitrogen cycle (ammonia → nitrite → nitrate) depends on beneficial bacteria in your filter. A filter should turn over the full tank volume 4–10 times per hour. Heavily stocked tanks or messy fish (goldfish, cichlids, plecos) need the higher end. Never clean the filter and perform a large water change simultaneously — you risk crashing your cycle by removing too much bacteria at once.
What's the key thing to understand about Community Tank Compatibility?
Beyond numbers, fish compatibility matters enormously. Fin-nippers (tiger barbs, serpae tetras) should not be kept with long-finned fish. Aggressive cichlids need significantly more space than peaceful community fish. Schooling fish should be kept in groups of 6+ of the same species. Bottom-dwellers (corydoras, loaches), mid-water fish (tetras, barbs), and top-swimmers (hatchetfish, danios) can share a tank without competing for the same space.
What should I know about Cycling a New Tank?
Never add fish to an uncycled tank. The nitrogen cycle takes 4–8 weeks to establish. Signs of completion: ammonia and nitrite both read 0, nitrates present. Fishless cycling (using ammonia directly) is the most humane approach. Once cycled, add fish gradually — adding too many at once overwhelms the biological filter. The first signs of an overstocked or uncycled tank are fish gasping at the surface and ammonia or nitrite spikes.