Moon Jellyfish

Photo: Wikimedia Commons (CC BY-SA)

Aurelia aurita

Identification	Translucent, disc-shaped medusa with four clearly visible horseshoe-shaped gonads (pink in females, white in males) visible through the bell. The bell margin is fringed with hundreds of short, hair-like tentacles and four longer oral arms hang below. One of the most recognizable jellyfish species in the aquarium hobby.
Maximum Length	Bell diameter 12–16 inches (30–40 cm)
Origin	Worldwide — found in coastal temperate to tropical ocean waters globally
Minimum Tank Size	Kreisel or flow-through jellyfish tank — minimum 10-gallon kreisel for small groups
Reef Compatibility	No — requires a dedicated jellyfish kreisel tank

Behavior

Moon Jellyfish require a specialized circular tank called a kreisel that creates a gentle, circular current keeping the jellies suspended without trapping them against walls or intakes. Standard aquariums will injure or kill jellyfish within hours. They are passive drifters — pulsing their bell continuously to maintain position. They can be kept in groups and are social. Their sting is mild and generally harmless to humans.

Diet & Feeding

Planktivore — feeds on zooplankton and organic particles using mucus on the bell and tentacles. In captivity: baby brine shrimp (Artemia nauplii), rotifers, copepods, and commercially prepared jellyfish foods. Feed once or twice daily.

Cautions

Requires a kreisel tank — cannot survive in a standard rectangular aquarium. Sensitive to poor water quality and temperature swings. Do not mix with fish or other invertebrates.