Razorfish (Shrimpfish)

Geographical Origin and Habitat: Tropical Indo-Pacific. It populates coastal coral reefs and sheltered lagoons. It has a strict symbiotic relationship with long-spined sea urchins (genus Diadema) or branching corals, taking refuge among their spines and branches to camouflage and protect itself.

Taxonomy and Morphology: Belongs to the Centriscidae family. Extremely laterally compressed body, almost flattened, armored by thin and transparent bony plates crossed by a distinct longitudinal dark stripe. The snout is tubular and elongated. The most striking feature is its swimming style: it lives constantly in a vertical, head-down position.

Social Behavior: Strictly gregarious and very shy species. In the wild it forms dense schools moving in perfect synchrony to confuse predators. In the aquarium it must be kept in a group of at least 5-7 specimens to prevent continuous fear and lethal stress.

Coloration and Sexual Dimorphism: Translucent/silvery body crossed by a marked dark line (black or dark brown) running to the tail, an adaptation for vertical camouflage among seagrass meadows or urchin spines. Sexual dimorphism is absent with no visible differences between sexes.

Aquarium Setup: Requires a mature marine aquarium of at least 200 liters (55 gallons), with live rock, caves and preferably macroalgae beds. The presence of long-spined urchins (even safe synthetic replicas) or branching corals (like gorgonians) is absolutely mandatory to offer them their instinctive vertical refuges.

Diet and Feeding: Specialized carnivore and micro-predator. This is the hardest aspect of its care. It feeds mainly on live zooplankton in nature. In captivity it requires copepods, amphipods, enriched brine shrimp nauplii, and live mysis. It requires multiple feedings (4-5 times a day) as it rarely accepts dry foods.

Water Quality: Excellent and stable tropical marine water. Temperature 23-28 °C (73-82 °F), specific gravity 1.020-1.026, pH 8.0-8.5. It requires moderate or gentle water flow, as strong currents would exhaust it due to its poor hydrodynamics and peculiar swimming style.

Compatibility and Cohabitation: Extremely peaceful but vulnerable. Cannot compete for food with fast or aggressive fish. Excellent companions are pipefish (Syngnathidae), small seahorses, or peaceful bottom-dwelling gobies. Triggerfish, puffers, large wrasses, and territorial damselfish must be strictly avoided.

Aquarium Breeding: Oviparous species with external fertilization. It releases eggs in open water, producing pelagic larvae. Captive breeding has been documented only in very few specialized public aquariums, due to the difficulty of feeding microscopic pelagic larvae with suitably sized plankton. Impossible in home aquariums.

Risks and Diseases: The main and fatal risk is death from starvation (malnutrition) or acute stress in the absence of a tight school or adequate refuges (urchins). It is also susceptible to classic marine parasites (like Oodinium and Cryptocaryon) and poorly tolerant to full doses of copper due to the absence of classic protective scales.