Jellyfish (or jellies as they are often known) are best described as free-swimming marine creatures consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for propulsion while tentacles can be used to capture prey.
Kept in the correct way, they are an entrancing addition to any location; calming, fascinating and mesmerising.
The lifecycle of jellyfish is as intriguing as the creatures themselves. The Medusa stage we know as jellyfish - being mature bell and tentacles - is only one small part of its lifecycle:
There are many species of jellyfish, and as with tropical fish, not all are compatible in the same enclosed space.
The most practical for keeping in a confined aquarium would be Moon Jellyfish, Blue Blubber Jellyfish, Upside-down Jellyfish, Flame Jellyfish and Amakusa Jellyfish, though with a little experience the world of jellyfish husbandry opens up to an abundance of varieties that offer a diverse and beautiful display.
Moon Jellyfish (Aurelia Aurita)
Moon jellies are the most common jellyfish to find in local aquatic stores. Yet common, moon jellyfish are one of the most popular species because of their opaque white colour and the relaxing movement.
This species is relatively easy to keep, and the husbandry for this species is well established. They usually come from cold to temperate waters and are bred commercially making them an ideal and environmentally friendly animal to keep, so it is recommended that you ask your dealer which strain of moon jellies they stock with preference shown towards more temperate strains. If cold water strains are kept, it will be necessary to have a chiller running on your aquarium. For temperate strains, this may not be required under ambient room temperatures of up to 22-24C as the aquarium will usually attain an average temperature a few degrees below this level.
Blue Blubber Jellyfish (Catostylus mosaicus)
Blue blubbers are also common species for jellyfish aquariums and relatively easy to keep. This species is distinguished by their dome shaped bell with eight oral arms which look like cauliflowers. They are strong and active swimmers with a distinctive rhythmic pulse that will add great variety to an aquarium shared with Moons.
They are popular by their variety of colours from light blue to dark purple and burgundy. There are sometimes white and brown colour variants as well, which are thought to depend on the species of symbiotic algae living inside their body. They are strong and active swimmers.
Upside-down Jellyfish (Cassiopea andromeda)
The upside down jellyfish is so called because it spends most of its time on mudflats with its bell against the sea bed and its tentacles pointed towards the water surface.
This jelly is one of the easiest species to keep as it does not require a kreisel system. They could be kept even in plastic bottles when they are small. The variation in their colour is one of their attractions, such as blue, green, orange and brown, usually with white stripes on their bells. Even though they are photosynthetic, they still require to be fed baby brine shrimp regularly to grow healthily.
Flame Jellyfish (Rhopelima esculentum)
From the Rhizostomae order (sometimes known as Rootmouth), the Flame Jellyfish is considered something of an expert's species, as its sting takes some managing while handling and aquarium cleaning, and the tank should not be shared with other jellyfish varieties.
Species of the Rhizostomae order have neither tentacles nor other structures at the bell's edges. Instead, they have eight highly-branched oral arms, along which there are suctorial minimouth orifices. (This is in contrast to other scyphozoans, which have four of these arms.) These oral arms become fused as they approach the central part of the jellyfish. The mouth of the animal is also subdivided into minute pores that are linked to coelenteron.
Amakusa Jellyfish (Sanderia malayensis)
From the Pelagiidae family, the Amakusa Jellyfish is found in the Indian Ocean and the North Atlantic waters. Considered something of an expert's species, its sting takes some managing while handling and aquarium cleaning, and the tank should not be shared with other jellyfish varieties.
The Amakusa jellyfish grows to a maximum diameter of around 9cm, naturally feeding on plankton and other jellyfish - especialy moon jellyfish - and brine shrimp. In captivity, specially formulated jellyfish food is recommended, with occassional live brink shrimp.
The Amakusa's tentacles are long - some up to 1 meter - and as such requires a large jellyfish aquarium to show at its best.
Spotted Jellyfish (Mastigias papua)
Spotted jellyfish (or lagoon jellyfish) inhabit quiet bays, harbours and
lagoons of the South Pacific. They are easily distinguished by the white spots throughout their body and the eight appendages hanging down from oral arms. They are very popular in aquarium trades for their variation of colour, which are pale blue, green, pink, orange and yellow, on their semi-translucent body covered with white spots.
Instead of single mouth, they have many small mouth openings on their oral arms, which capture small zooplankton. As they depend on the photosynthesis by symbiotic algae for their energy requirements, full spectrum lighting is required in aquariums.
Comb Jellyfish (Mastigias papua)
Common species for comb jellyfish are Cydipidda (sea gooseberries), Lobata and Beroida. They are not common for aquarium market but their delicate beauty continues to fascinate people around the world. Species in Cydipidda and Lobata are fed with live baby brine shrimp, and Beroida needs to be fed with other ctenophore jellyfish. Their fragile body makes keeping them in captivity hard. They could be kept in captivity for at most 3 months in a kreisel system with good care.
Read or download our introduction to jellyfish, authored by Alan Adler of Glass Ocean and published in the highly respected UltraMarine Magazine (issue 48; October 2014)