Citron Goby

With its bright lemon-yellow body and thin electric blue lines across its head, the citron goby is the best-known species of the group known as "coral gobies" or "clown gobies" (Gobiodon). With its short, laterally compressed body it prefers perching to swimming; it spends most of its day among the branches of a branching coral. It is distinguished from the yellow clown goby (Gobiodon okinawae), which has its own page on this site, by its larger size and the blue lines on its head.

Its skin secretes a bitter, toxic mucus; this secretion makes it unpalatable to predators. It does not harm other fish in the aquarium, but a dead specimen can foul the water in a small aquarium. It is a species that can be bred in the aquarium; captive-bred specimens take to dry food more easily.

It lives on reefs at depths of 2–20 meters in the Indo-West Pacific, from the Red Sea to Samoa. Its life is tied to branching Acropora colonies: it lives alone or in pairs among the branches of a colony, feeding and spawning there. It feeds on small invertebrates and plankton.

• Volume: At least 40 liters for a pair; suitable for nano reef aquariums.
• Water: Salinity specific gravity 1.023–1.026, pH 8.1–8.4, temperature 24–27°C; low nitrate.
• Reef compatibility: Reef-safe with caution. It leaves shrimp and snails alone, but some specimens pick at the polyps or branch bases of Acropora and other SPS corals. Small SPS frags are at risk.
• Layout: Branching corals or sturdy branched rock structures where it can perch.
• Lid: Like other gobies it can jump; a covered aquarium is recommended.

Carnivorous. Small frozen foods (mysis, enriched brine shrimp, copepods) and fine granules should be the staple. Because it eats slowly and timidly, release the food near the coral where it sits. Offer small amounts at least twice a day.

Peaceful and calm. It does not bother other fish, but in a small aquarium it can be quarrelsome towards unfamiliar members of its own species and other Gobiodon species. It considers the coral it perches on its own territory.

Good companions: Clownfish, neon goby, firefish, cardinalfish, small blennies, cleaner and other ornamental shrimp.

Avoid: Predators such as hawkfish, dottybacks, large wrasses and lionfish; other Gobiodon species in the same aquarium.

Kept singly or as a pair. A mated pair is the best option; two unfamiliar adults fight in a small aquarium. In a large aquarium, if there are enough branching corals, more than one pair can live together.

It spawns frequently in the aquarium. The pair sticks its eggs under a branch of the coral it perches on; the male guards the eggs. Coral tissue may recede in the area where the eggs are laid; for this reason, keep an eye on the pair in SPS aquariums. The fry are planktonic and are fed rotifers in the first days.

• Captive-bred specimens are hardy; quarantine is more important for wild specimens.
• Marine white spot and velvet: Quarantine new fish for 3–4 weeks.
• Wasting is usually caused by insufficient feeding; faster-eating fish may snatch the food.

There is no reliable external difference. Sex change is known in Gobiodon gobies; two individuals that come together usually form a pair. The belly of a female carrying eggs becomes fuller.