Also Known As: Masked Spinefoot, Blue Lined Rabbitfish

Compatibility and Behavior
The Masked Rabbitfish (Siganus puellus) is a gorgeous, intricately patterned member of the Rabbitfish family. A golden yellow to yellow-orange body grades through pale blue into silvery white along the belly, overlaid with a maze of fine wavy blue lines that run vertically toward the head and shift horizontal toward the tail, an effect often compared to circuit-board scribbling. Its namesake feature is the blackish diagonal bar sweeping from the chin up through the eye to the nape. 
Note on stress coloration: like other rabbitfish, it can drop that bright patterning in seconds and switch to drab mottled camouflage while sleeping or startled, so a suddenly dull fish is typically just resting, with color returning as it settles. This is a more open-water species than most rabbitfish, an active, peaceful grazer that works the rockwork for algae all day. Reef compatibility comes with a caveat: a well-fed specimen in an appropriately large tank is generally trustworthy with corals, but underfeeding or cramped quarters may lead it to nip LPS polyps, soft corals, sponges, tunicates, and macroalgae, so steady greens and adequate space are the real safeguards. It will also readily eat ornamental macroalgae, so a planted Caulerpa display is a poor pairing. Fish compatibility is easy, since their venomous spines earn respect, and adults hold their own alongside large angels, tangs, wrasses, and even triggers, while smaller tankmates are typically left alone in a spacious system. The firm rule is no other rabbitfish or foxfaces. Handling calls for genuine caution, as the dorsal, anal, and pelvic spines are venomous and can inflict a severely painful sting, so wear gloves and move the fish in a rigid container rather than a net.

Aquarium Requirements
Small specimens can be grown out in a 75 gallon tank, but this species reaches a substantial size and roams widely, so a permanent home of 150 gallons or larger with at least 18 inches of width is what it genuinely needs. Tank size is a husbandry issue here rather than a luxury, since a confined adult tends toward more aggression and more coral nipping. Build around long, unobstructed swimming lanes fronting mature live rock that provides both grazing pasture and crevices to wedge into overnight. A sand substrate suits it, moderate flow with strong surface agitation mirrors its seaward reef-slope habitat, and medium to strong lighting encourages the algae film it grazes. Supplement grazing with dried nori or Ulva on a clip at least three times a week, along with spirulina flakes, algae wafers, and prepared herbivore foods, offering meaty items only occasionally. A secure lid is recommended, and a specimen container is safer than a mesh net for moves.

Specifications
Approximate Size: 2–3.5"
Diet: Herbivore; dried nori and Ulva on a clip, spirulina flakes, algae wafers, and prepared herbivore preparations, supplemented by natural algae grazing on live rock, with occasional meaty frozen foods, fed 2–3 times daily
Origin: Indo-West Pacific
Care Level: Moderate
Reef Safe: With caution
Temperament: Peaceful
Special Considerations: Venomous dorsal, anal, and pelvic spines can inflict a severely painful sting, so handle with care and move it in a rigid container rather than a net. Reef safe with caution, as an underfed or cramped fish may nip corals and will eat ornamental macroalgae.