The Jelly fish is a very interesting invertebrate related to corals and plankton. They 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.
They sting their food with nematocysts, paralyzing it, and bringing it into its mouth with its tentacles. Many swimmers run into this each year as well. Many of them think that it is a defensive behavior, in reality, they just happened to be in the way and handled as any other things that might come along to be feed the Jelly fish.
The largest killer of the ocean is not a shark. It is a Jelly fish common in Australia called the Box Jelly. Though the shark gets all the credit, it by far kills less each year than this regional jelly.
Keeping a Jelly fish in an aquarium is not as easy as many other marine lives. The Jelly fish has special needs, and should only be kept by advanced Aquarists.
For example, in the wild the Jelly fish knows no walls. They would probably be in trouble, as it would not do well for their shape. You have to use special Kreisel tanks that are cylinder shaped. This way there are no corners to get caught in. Another aspect of jellyfish aquarium tanks is that the water has to flow in special ways, to prevent sucking the Jelly fish to its demise.
There are other special considerations in terms of water flow that needs to be made as well. Jelly fish require a constant flow in the wild. This helps it and its food to meet. It is also likely that it helps carry off waste.
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 sea horse tanks.
Jelly fish are made up like nearly no other marine life you have seen. It is symmetrical based around some radial point. There is often very little actual organic content, since 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 Jelly fish 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 (sexually). They are then released into the water from the female’s mouth. This eggs leaves the mouth of the somewhere dark) to attach themselves and change into a polyp. The polyp will divide itself creating new polyps (asexual reproduction) it will eventually divide and the parts will be ephyra (young adult medusa) and grow to a full size adult. Most Jelly fish 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) Jelly fish is the Moon Jelly fish (Aurelia aurita). The Moon Jelly fish 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. It is usually found in peaceful bays and harbors.
In captivity, it is often fed live brine shrimp larvae, in large quantities. You will probably have to breed your own to keep up with it. Reminder, keeping a Jelly fish is not for the inexperienced, or the cheap. The sting of this Jelly fish is mild compared to others, and relatively harmless to people. However, you should take care as allergic reactions can still occur.
They come from colder waters. 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 Jelly fish might be ideal for an underground basement tank.
Another popular Jelly fish is the Upside Down Jelly fish (Cassiopea) that comes from the western Pacific Ocean around the Philippines, and has been introduced to Hawaii as well (probably by ship around world war II). They grow to about 8 inches /20 cm in diameter. They are interesting because they often lay on the bottom of sandy flats in shallower water though they sometimes float around. It carries symbiotic algae for food and swimming upside down allows that algae to catch the rays of the sun it needs for photosynthesis. It also feeds on micro plankton like most other Jelly fish.
The Cassiopea Jelly fish in captivity are by far the most common jelly fish species in aquariums and can occasionally be found in pet stores. To keep Cassiopea Jelly, you will need an upwards water flow to allow the jellyfish to be suspended.
The filtration demands of the Jelly fish will resemble those of a reef tank. The water quality must be very good for your Jelly fish to live well. Multiple skimming (surface and protein) is a strong suggestion. 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 Jelly fish’s sting, and likely to harm a lot more than just that in the Jelly fish. You will also want decent mechanical filtration.
The next big hurdle is feeding them. 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 Jelly fish depends on strong rays to photosynthesize. Metal Halide, and/or VHO lighting are highly recommended.
Now, if you are not discouraged from keeping Jelly fish in your aquarium, good luck. Just remember that it will be more challenging (and rewarding) than some 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,” you will want to seek medical attention. While the two here mentioned are suggested as “safe,” it is possible to have an allergic reaction that is much worse. Be safe out there!
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