TankBud

Yellow boxfish

Ostracion cubicus

Also known as Cube Boxfish, Cubicus Boxfish, Polka-Dot Boxfish

SaltwaterFish

Yellow boxfish (Ostracion cubicus)
portioid · CC BY-SA 4.0

Care at a glance

Temperature
75–81°F
24–27°C
pH
8.1–8.4
Adult size
17.7 in
45 cm
Minimum tank
250 gal
946 L
Temperament
Peaceful
Social behavior
Solitary
Tankmates
With caution
Swim level
Bottom
Diet
Omnivore
Difficulty
Difficult
Breeding
Hard
Rarity
Common
Reef safe
Not reef safe
Family
Ostraciidae
Origin
Indo-Pacific reefs, from the Red Sea and East Africa to Hawaii and the Tuamotus

Overview

The yellow boxfish is a slow, boxy reef fish, often described as having real personality once it settles in. It is an expert-only fish.

Did you know

The yellow boxfish's hexagonal-plated shell inspired the Mercedes-Benz Bionic concept car of 2005, which borrowed its boxy proportions for a low drag coefficient. Later research found that the fish's own shape is not quite as aerodynamic as the designers first assumed.

Caring for the yellow boxfish

Keep a yellow boxfish in a large, mature, stable tank of at least 250 gal (946 L), never a new one. It needs that room for its adult size, and it does poorly in anything less than excellent, stable water quality. Hold the water at 75 to 81°F (24 to 27°C) and a pH of 8.1 to 8.4.

It is not reef safe, since it picks at coral polyps, tubeworms and small invertebrates. Feed live brine shrimp or mysis at first. Once it settles in, move on to chopped clam, squid, mussel and marine algae.

The yellow boxfish is peaceful and more likely to be picked on than to start trouble, so choose its tank mates with caution. Keep it alone, since two boxfish rarely tolerate each other and any aggression or injury raises the risk of a toxin release. Breeding it is hard.

A badly stressed or dying boxfish releases its toxin into the water. In a closed aquarium that toxin can wipe out every other fish before anyone notices something is wrong. The risk also makes it a poor match for a tank full of animals that cannot be evacuated in an emergency. Have a plan for emergency water changes and carbon filtration if it ever looks stressed.

Good to know

The yellow boxfish is a member of the family Ostraciidae, also known as the cube, cubicus or polka-dot boxfish. Unlike true puffers, it has small, individual conical teeth rather than a fused beak. It nips at sponges, tunicates, algae and small invertebrates instead of crushing shells. Its real defense is a rigid carapace of fused hexagonal bone plates under the skin. Glands in its skin release its toxin, ostracitoxin, which is also known as pahutoxin.

In the wild

The yellow boxfish is found on Indo-Pacific reefs from the Red Sea and East Africa to Hawaii and the Tuamotus. It usually lives in lagoons and on shallow coral reefs less than 50 m deep. Juveniles are bright yellow with bold black spots and stay close to branching coral for cover. Adults range more openly over reef and rubble.

Common questions

What size tank does a yellow boxfish need?

A yellow boxfish needs at least 250 gal (946 L). It spends most of its time in the bottom.

What temperature and pH does a yellow boxfish need?

A yellow boxfish is comfortable at 75–81°F (24–27°C) with a pH of 8.1–8.4.

What does a yellow boxfish eat?

A yellow boxfish starts on live brine shrimp or mysis. Once it settles in, it eats chopped clam, squid, mussel and marine algae.

How big does a yellow boxfish get?

An adult yellow boxfish reaches about 17.7 in (45 cm).

Related species