How Many Fish in a 20 Gallon Saltwater Tank?
Saltwater stocking is more conservative than freshwater — marine fish need more room, produce more waste, and many are territorial. The calculator below is pre-set to 20 gallons (saltwater); add your livestock and it'll flag reef-safe, aggression, and tank-size problems.
Example 20-gallon saltwater stocking ideas
- Nano reef: 1 ocellaris clownfish + a neon goby + a cleaner shrimp and a small cleanup crew.
- Clownfish nano: a bonded clownfish pair in a soft-coral reef.
- Goby-blenny nano: a tailspot blenny + firefish + snails and hermits.
Cycle the tank fully, add the most peaceful fish first and the most aggressive last, and quarantine new arrivals. Run your exact list through the calculator above.
Reef fish for a 20-gallon saltwater tank
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