What can your saltwater tank hold?
A marine stocking calculator that checks bioload, reef-safe status, aggression, and tank-size needs (tangs, angels, and more) — so your reef thrives. Free, no signup.
Saltwater Stocking Calculator
Plan a reef or FOWLR tank with reef-safe and aggression warnings.
Open toolHow many fish in a saltwater tank?
Pick your reef tank size for stocking ideas and a calculator pre-set for you:
Popular saltwater aquarium fish
Photos via Wikimedia Commons under their respective licenses — click a credit for the source.
Frequently Asked Questions
How is saltwater stocking different from freshwater?
Marine systems hold far less livestock per gallon and care much more about aggression, territory, and reef-safe status. Many popular fish (tangs, large angels) need big tanks. Our calculator weighs all of this rather than using volume alone.
What does "reef-safe" mean?
A reef-safe fish can be kept with corals and invertebrates without eating or nipping them. Some fish are reef-safe "with caution" (individuals vary), and others are only suitable for fish-only (FOWLR) tanks. The calculator flags each one.
Do I need a protein skimmer and RO/DI water?
For a reef, effectively yes. A protein skimmer exports waste before it breaks down, and RO/DI (purified) water mixed with a quality salt avoids introducing nutrients and contaminants. They are the backbone of a stable marine system.