Japanese Sea Nettle (Chrysaora pacifica)

Easily identified by the bold, reddish-brown stripes radiating from the center of its bell, the Japanese sea nettle (Chrysaora pacifica) is a striking jellyfish, native to the cold to temperate coastal waters of the northwest Pacific of Japan and Korea. Its translucent, pale bell can reach 30 cm in diameter, contrasting with its long oral arms and trailing tentacles. While its sting is rarely dangerous, it can be intensely painful, especially on sensitive areas. Known for its rhythmic, ghostly pulsations, this elegant cnidarian, accentuated by its vivid markings, is a captivating spectacle in aquariums.

Notes: The Japanese sea nettle presents specific challenges in captivity, primarily due to its specialized diet. It has a relatively high dependency on fish larvae and other gelatinous organisms; a diet of solely baby brine shrimp is nutritionally inadequate and often leads to the jellyfish shrinking and failing to thrive. Consequently, achieving a bell diameter exceeding 10 cm in an aquarium is notably difficult. To display their signature elegance, they must be kept in large, low-density kreisel tanks. This spacious setup prevents their delicate tentacles from tangling or damaging, allowing them to extend fully and showcase their graceful, flowing movement.

Their polyps and ephyrae are easily maintained at 18-20°C on a diet of freshly hatched brine shrimp. Strobilation can be initiated by lowering the temperature to 13-15°C. The ephyrae can feed on newly hatched brine shrimp from day one, and are relatively easy to grow. The juveniles are sticky and often adhere to aquarium walls. If a juvenile becomes stuck, it must be gently detached immediately. Failure to do so will cause it to become inverted. For the same reason, they must be separated gently as soon as they are found tangled.