The Jelly fish is a fascinating invertebrate related to corals and plankton. Most species of jellyfish are brainless, spineless, stomach less, and eyeless. Yet, they survive floating in the ocean. Some species wait for their food to float to it, while others move around more to get their food.
Jelly fish sting their food with nematocysts, paralyzing it, and bringing it into the mouth with the tentacles. Many human swimmers are subjected to jellyfish sting each year as well. It is easy to think that it is a defensive behavior, but in reality, a stung swimmer just happened to be in the way and was handled as any other thing that might come along. The largest killer of the ocean is not a shark – it is a jellyfish common in Australia and Hawaii called the box jellyfish or sea wasp. Though the shark gets most of the media attention, it kills much fewer humans each year than this dangerous jellyfish.
Keeping a jelly fish in an aquarium is not as easy as many other marine creatures. The jelly fish has special needs, and should only be kept by advanced aquarists. For example, in the wild the Jelly fish never encounters everlasting glass walls and can therefore become “trapped” in the corners of ordinary rectangular aquariums. The safest course of action is to use cylinder shaped tanks without any corners for the jellyfish to get stuck in. Another aspect of jellyfish keeping is that the water has to flow in special ways, and the filter mustn’t be able to suck the jellyfish in. There are other special considerations in terms of water flow that needs to be made as well. In the wild, many species if jellyfish relays mainly on currents to transport them around, bring them food and remove their waste products.
With that in mind, you will likely have to look for different aquarium tank suppliers to find what you need to successfully keep jellyfish in aquarium. There are a few online stores so far that carry aquariums and equipment for keeping jellyfish. You will unlikely be able to find them at the local fish store. You might also be able to find some instructions regarding building your own, though pay special attention to the water flow if you do that. They are similar to seahorse tanks.
Jellyfish are quite extraordinary when it comes to anatomy and clearly distinguishes themselves from most other aquatic creatures. The body of a jellyfish is symmetrical and based around a radial point. There is often very little actual organic content, since a jellyfish is over 95% water. They have an outer skin of a sort, and an inner layer. Between the two is the jelly like substance.
A true jellyfish goes thru a 5-stage life cycle. This begins when the full-grown female medusa’s gonads form and hold the eggs. The male releases sperm which then floats into the female’s mouth and fertilizes the eggs (sexual reproduction). They are then released into the water from the female’s mouth. Eventually, the young creatures will attach themselves and change into polyp. The polyp will divide itself creating new polyps (asexual reproduction). It will also eventually divide and the parts will be an ephyra (young adult medusa), that gradually grows into a full size adult. Most jellyfish live only three to six months, but can reproduce in large numbers during this short life. A few species are known to live as long as 2-3 years.
One of the most commonly found (worldwide) jellyfish is the Moon Jellyfish (Aurelia aurita). The Moon Jellyfish that is also popular in large sea aquariums. It can be found from temperate to tropical ranges, and grows to about 12 inches/ 30 cm in diameter. In the wild they eat micro plankton and occasionally small fish larvae. They are usually found in peaceful bays and harbors.
In captivity, the Moon Jellyfish is usually fed live brine shrimp larvae, in large quantities. You will probably have to breed your own brine shrimp to keep your jellyfish satisfied. Keeping a jellyfish is neither for the inexperienced, nor for people with very little time and/or money to spend on their hobby. The sting of a Moon Jelly fish is mild compared to many other species and relatively harmless to people. However, you should take care as allergic reactions can occur.
Moon Jellyfish hail from colder waters than tropical aquarium fish. If you cannot keep the water temperature from 55 to 65 degrees F / 12-18 degrees C by having a low room temperature, you will likely need to get a refrigeration unit to cool the water. This jellyfish can be ideal for an underground basement tank where the temperature is low year round.
Another popular Jelly fish is the Upside Down Jelly fish, Cassiopea, which comes from the western Pacific Ocean around the Philippines and has been introduced to Hawaii (probably by ships around World War II). Cassiopea grows to about 8 inches / 20 cm in diameter. They are interesting because they often lay on the bottom of sandy flats in shallower water, but they are also capable of floating around. The Upside Down Jelly fish carries symbiotic algae for food and swimming upside down allows that algae to catch the rays of the sun necessary for photosynthesis. Cassiopea also feeds on micro plankton like most other Jelly fish.
Keeping Cassiopea jellyfish in captivity is comparatively common and this species is by far the most frequently kept jellyfish species among aquarists. It can occasionally even be found in ordinary pet stores. To keep Cassiopea jellyfish you will need an upwards water flow to allow the jellyfish to stay suspended close to the surface.
The filtration demands of the jelly fish will resemble those of a reef tank. The water quality must be very good for your jellyfish to live well. Multiple skimming (surface and protein) is strongly suggested. Very effective biological filtration is important and ammonia content should be kept at the lowest levels humanly possible. Ammonia is known to neutralize the poison of a jellyfish’s sting, and is believed to harm a lot more than just the venom in a jellyfish. You will also want decent mechanical filtration when keeping jellyfish in an aquarium.
The next big hurdle is feeding your jellyfish. They eat live plankton and a few other things in the wild. Again, you will have little luck on good supply from the local fish store. One thing often used (though not as good as their natural diet) is baby brine shrimp (1-2 days old) which can be hatched in large quantities. Plan on a second hobby in raising Brine shrimp.
And the final note, LIGHTING! Your Upside Down Jellyfish fish depends on strong rays for its symbiotic algae to photosynthesize. Metal Halide, and/or VHO lighting are highly recommended.
Now, if you are not discouraged from keeping jellyfish in your aquarium, good luck. Just remember that it will be more challenging (and rewarding) than most other marine life.
On a safety note… If stung, there are a number of means suggested to cool the sting, including ammonia and vinegar. If this does not help or you feel other effects that are above a “sting,” seek immediate medical attention. While the two species suggested above are condsidered “safe” for humans, it is possible to have an allergic reaction that is much worse than the normal symptoms. Always handle your jellyfish with great care to keep both of you happy and healthy!
Box jellyfish aka Sea wasp - information about Box jellyfish aka sea wasp
Cannonball Jellyfish - information about Cannonball Jellyfish
Erenna Jellyfish - information about Erenna Jelly Fish
Freshwater Jellyfish - Information about freshwater Jellyfish
Jellyfish Facts - A few facts about jellyfish
Moon jellyfish - information about Moon jellyfish
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