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Thompson's Surgeonfish

Acanthurus thompsoni

Marine Marine Indo-Pacific

Unlike most surgeonfish that graze benthic algae, this uniform slate-grey tang primarily plucks zooplankton from the open water column near drop-offs. It is reef-safe and unaggressive toward unrelated fishes, but demands strong hydrodynamic current, high oxygenation, and considerable longitudinal swimming room.

Also called: Chocolate surgeon, Chocolate surgeonfish, Kandu kaalhu.

23 cm adult length, drawn to scale. deep body.

Saltwater species. The planner judges it with a marine rule set. A reef or fish-only tank takes months to mature and costs more to run than freshwater. See the marine page.

Try it in the planner Opens a tank sized to its minimum with 1 fish added.

What it needs

ItemValueBecause
Adult length 23 cm Used for the Space check: the tank must be long enough for the fish to turn round.
Smallest tank 600 L, at least 180 cm long estimated The least water and floor length this species is kept in for good, as a single fish or smallest group.
Extra water per added fish 100 L estimated What each further fish adds once the minimum is met.
Waste load Class 4 of 5 estimated How much waste an adult makes against its size. Feeds the Load check.
Temperature 23 to 27 C Stock sharing a tank need overlapping ranges.
pH 8.1 to 8.4 Compared with tankmates in the Water check.
Hardness GH 8 to 12, KH 8 to 12 Degrees of general and carbonate hardness.
Flow High Low-flow fish are stressed in a strong current.
Light Moderate Matched to the lighting class on the needs sheet.
Group size Single fish is fine Not a schooling species.
Temperament Peaceful Territorial: weak.
Swims in All levels Fish that use different levels share a tank more easily.
Lifespan About 12 years A fish is a long commitment.
Experience Some experience helps A guide to how forgiving the species is of mistakes.
Jumps Yes Keep the tank covered.
Salinity Marine, about SG 1.023 to 1.025 Needs salt water, a different build and a longer-running tank than a freshwater set-up.

Tags marked estimated are judged from the size and habits of the species rather than measured, so treat them as a sensible default.

Diet and tank layout

Thompson's Surgeonfish is an plankton feeder that swims in all levels of the tank. It is safe with plants. Give it some cover.

Tankmates

Works with

Depends

Avoid

Compare any two fish on the compatibility page, or print the equipment for a stock on the needs sheet. How this is worked out: the method.