Crab

Arrow crab

Stenorhynchus seticornis

Group: Crab
Care level: Intermediate
With corals: Reef safe with caution

What does the arrow crab do in a reef tank?

Bristleworms (can wipe them out), other worms, small fish

With corals: With caution

How many should you keep?

Never more than one per tank

One US gallon is 3.785 litres and one UK gallon is 4.546 litres, so a "per gallon" rule depends on whose gallon it means.

What can go wrong?

Territorial; eats small fish and worms

Which tankmates are risky?

Fish

Fish that may eat or harass it.

Take care (4)

Neon gobyThe arrow crab can catch small fish like the neon goby.
Yellow clown gobyThe arrow crab can catch small fish like the yellow clown goby.
Hi-fin red banded gobyThe arrow crab can catch small fish like the hi-fin red banded goby.
Yellow assessorThe arrow crab can catch small fish like the yellow assessor.

Other invertebrates

Invertebrates it may harm, or that may harm it.

None known.

These checks follow the reasons fish and invertebrates clash: same species or genus, similar shape, mouth size, temperament, food, burrows, tank size and the order they are added. Individual animals differ; every source agrees on that.

Sources

Practical Fishkeeping (UK), essential cleaners for the reef tank (date not shown)Read 21 October 2026, read in full.

Last checked 21 October 2026. How we check

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