Moon jellyfish (Aurelia aurita) care guide

Group
Other invertebrates
Other names
Moon jelly, Common jellyfish, Saucer jellyfish, Northern moon jelly, Aurelia sp.
Family
Ulmaridae
Origin
North-east Atlantic including the Baltic and British coasts; introduced to the north-east United States and Argentina
Water
saltwater
Maximum size
30 cm
Temperature
16–26°C
pH
8.1–8.4
Hardness
SG 1.023–1.025, dKH 8–12
Care level
intermediate
Reef safe
no
Flow
Gentle circular laminar flow (kreisel tank)

Care

The moon jellyfish is a nearly transparent jellyfish with four horseshoe-shaped gonads showing through the top of its bell, which is usually 25–40 cm across in the wild; aquarium jellies stay much smaller, up to about 30 cm. It drifts with the current, pulsing gently, and its short fine tentacles give only a mild sting that most people barely notice. Names: until the 2020s Aurelia aurita was treated as a single worldwide species, but it has been split into at least 28 near-identical species that need genetic testing to tell apart. Many moon jellies sold, especially from the Pacific, are probably other Aurelia species. Native species: Aurelia aurita is native to the seas around Britain. Wild jellies should not be collected from the wild where that is not allowed, and captive animals must never be released. Set-up: jellyfish need a dedicated jellyfish tank, not a normal aquarium. A kreisel or similar tank has rounded corners and gentle, circular, laminar flow that keeps the jellies suspended, with screened intakes so they cannot be sucked in. No decor with sharp or rough edges, and no air bubbles, which get trapped under the bell and cause holes. Keep at room temperature (about 16–26 °C); a chiller may be needed in a hot room. Water: pH 8.1–8.4, SG 1.023–1.025, dKH 8–12, very stable. Copper: copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most other invertebrates. Never dose them in a tank holding this animal, and read the label of any treatment, fertiliser or algae remover before use. Sources: LiveAquaria (liveaquaria.com/products/moon-jellyfish); Wikipedia (en.wikipedia.org/wiki/Aureliaaurita). Checked October 2026.

Diet

A carnivore that catches plankton, copepods, small jellies, mollusc larvae and fish eggs with its tentacles. Feed newly hatched brine shrimp, rotifers or neutrally buoyant jellyfish foods one or more times a day, and change water often to remove waste.

Breeding

The jellyfish (medusa) spawns sexually, producing larvae that settle as tiny polyps. Polyps multiply asexually and can survive months without food; seasonal temperature changes trigger them to strobilate, budding off tiny baby jellies called ephyrae. Food supply affects the young: well-fed polyps produce many small offspring and poorly fed ones fewer, larger and hardier offspring. Hobbyists can raise polyps and ephyrae with patience, but most buy jellies or polyp cultures.

Compatibility and tank mates

Not reef compatible and not to be mixed with fish, corals or pumps of an ordinary aquarium. Keep only with other moon jellies.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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