Reef Tank Stocking Calculator
Calculate how many fish your tank can hold and get personalized stocking recommendations.
Tank Size
Common sizes: 20g, 40g, 55g, 75g, 90g, 120g, 180g
Current Fish
Clownfish
Tangs
Wrasses
Gobies
Damsels
Angels
Other
Bioload Status
Enter your tank size to see results
Total Fish
Tank Size
Things to consider
Capacity used:
Conservative
Moderate
Maximum
Understanding Fish Stocking in Reef Tanks
A Modern Approach to Stocking
Forget the old "inch-per-gallon" rule — it doesn't account for the unique needs of saltwater fish. Modern reefkeepers focus on species-specific requirements:
- Minimum tank size: Each species has a recommended minimum based on swimming patterns, territory needs, and adult size. A Yellow Tang needs 100+ gallons not because of bioload, but because it needs room to swim.
- Territory and aggression: Some fish claim space regardless of tank size. Multiple tangs or angels need significantly more room than the sum of their individual requirements.
- Bioload capacity: Your filtration (skimmer, refugium, rock) determines how much waste your system can process — not a simple fish-to-gallon ratio.
This calculator uses minimum tank requirements from our fish database to give you realistic guidance, not outdated formulas.
Factors Beyond the Numbers
This calculator provides guidelines, but other factors matter:
- Fish body shape: A 6" tang produces more waste than a 6" firefish
- Filtration capacity: Skimmers, refugiums, and biological media affect capacity
- Feeding habits: Heavy feeders need more space
- Territory requirements: Some fish need space regardless of bioload
- Swimming needs: Active fish like tangs need more horizontal space
Tips for Successful Stocking
- Add fish slowly - one or two at a time with weeks in between
- Quarantine new fish before adding to your display
- Consider compatibility and aggression levels
- Add more aggressive fish last
- Monitor water parameters closely when adding new fish
