Upside-down jellyfish (Cassiopea andromeda) care guide

Group
Other invertebrates
Other names
Andromeda jellyfish, Cassiopea jellyfish
Family
Cassiopeidae
Origin
Tropical Indo-Pacific and Red Sea; spread into the Mediterranean and Hawaii; shallow lagoons, mudflats and mangroves
Water
saltwater
Maximum size
30 cm
Care level
intermediate
Reef safe
with_caution

Care

The upside-down jellyfish rests bell-down on sand or mud with its frilly oral arms facing upwards, pulsing gently. It reaches about 30 cm across. Its brown, green or bluish colour comes from symbiotic algae (zooxanthellae) in its tissues. Light: because its algae supply much of its food, it needs strong lighting, as for light-hungry corals, and should sit on open sand where the light reaches it. It lives on shallow sand and mudflats, in lagoons and around mangroves. In the aquarium give it a dedicated tank or a sand-bottomed refugium with gentle flow and covered pump intakes; it cannot cope with strong powerheads. Our sources give no water figures for this species. Sting: it can give a painful sting with rash and swelling; it releases stinging mucus into the water, so wear gloves when working in its tank. 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 check the label of any treatment or fertiliser before use. Sources: Wikipedia (en.wikipedia.org/wiki/Cassiopeaandromeda). Checked October 2026.

Diet

Fed largely by its zooxanthellae under strong light; it also catches small animals with stinging cells and mucus. Feed small amounts of live or frozen baby brine shrimp, rotifers or fine zooplankton foods a few times a week.

Breeding

The medusa (jellyfish) stage reproduces sexually: females hold their eggs and catch sperm from the water. The larvae settle as tiny polyps that bud off more polyps and, in time, new jellyfish. Polyps often appear in aquaria, so it can be bred in captivity.

Compatibility and tank mates

Reef safe with caution: it can sting corals and fish that touch it, and its stinging mucus can irritate tankmates. Fish that pick at jellyfish (angelfish, butterflyfish, puffers, triggers) will damage it. Best in a species tank or refugium.

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

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