How to make a jellyfish tank

Written by brenton shields
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How to make a jellyfish tank
A proper jellyfish tank must have strong filtration yet a soft current as to not damage their delicate bodies. (John Foxx/Stockbyte/Getty Images)

Jellyfish are not very common in home aquariums and for good reason: their demand for high-quality water, perfect lighting, and delicate yet strong filtration and finicky eating habits make them extraordinarily difficult to care for. Setting up a proper jellyfish tank is the first step in successfully keeping common jellyfish species like Moon jellies or Upside Down jellyfish. Be warned that a jellyfish tank should be exclusively for jellyfish and anyone thinking about jumping into jellyfish care should at least have some prior experience with saltwater aquariums.

Skill level:
Moderately Challenging

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Things you need

  • Glass aquarium, spherical, 20-plus gallons
  • Internal sponge filter with activated carbon and vertical bubble tube
  • VHO metal halide lighting (about 8 watts per gallon, bulb and fixture)
  • Aquarium gravel
  • Glass marbles
  • Hydrometer
  • Aquarium salt
  • Adjustable heater
  • Dechlorinating agents

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  1. 1

    Place the spherical aquarium in an area where it will not receive a lot of direct sunlight. The light will be provided by the VHO (Very High Ouput) lighting you install later on. Too much direct sunlight will cause a detrimental algae bloom. The tank must be spherical because jellyfish will get stuck in the corners of a standard cubical aquarium.

  2. 2

    Rinse out the aquarium gravel under some freshwater to remove any dust and debris, and then place an inch-deep layer it at the bottom of the aquarium. The gravel, which should be somewhat angular and porous, will provide surface area for the growth of beneficial bacteria.

  3. 3

    Rinse the glass marbles under freshwater to remove any dust or dirt and layer them over top of the gravel. Provide about an inch deep layer. The layer of marbles will prevent the delicate jellyfish from scraping themselves on the angular gravel.

  4. 4

    Construct the sponge filer according to the specific manufacturer's directions. The filter should be an internal filter, meaning that it is completely enclosed within the aquarium as to not create turbulent currents when expelling clean water. Ideally, the filter should have a circular base, which contains the sponge and activated carbon (filter medium) and a vertical bubble tube that expels the cleaned water. However, the construction of internal filters will vary. Just make sure that the filter is internal (ask your local pet shop employee) and more than powerful enough for the size of the aquarium, since the water will need to be kept very clean.

  5. 5

    Place the filter in the centre of the aquarium by twisting the base into the gravel. Run the filter's power chord up along the vertical bubble tube and out the top of the aquarium. As a tip, you can wrap the chord around the bubble tube on the way up so that it is secure.

  6. 6

    Fill the tank with freshwater and add aquarium salt. Use the hydrometer to measure the salinity by filling the hydrometer's beaker with water and observing where the floating needle inside points. Ideally, the salinity of the water should read at about 1.024ppt (parts per trillion). If it is too low, add more salt. If it is too high, dilute it with freshwater.

  7. 7

    Place the adjustable heater within the aquarium and set it to exactly 23.9 degrees Celsius. The exact temperature for jellyfish will vary depending on the species, as some, like Moon jellies, prefer colder temperatures of around 18.3 degrees Celsius.

  8. 8

    Place the light fixture over the aquarium and keep the lights on at least twelve hours a day. The light should be VHO metal halide and provide about 8 watts per gallon of water. The lighting requirements for jellyfish are very similar to reef tanks. You may consider using a timer for the lights so you do not have to manually turn them on and off every day.

  9. 9

    Power on the filter and add proper dechlorinating agents. These come as liquids and remove harmful chemicals like ammonia and chlorine. Wait at least a month for the tank to cycle, leaving the filter on, before adding any jellyfish.

Tips and warnings

  • Jellyfish should be fed brine shrimp and small plankton, all of which can be purchased either from local pet shops or online.
  • Place one jellyfish in the tank at first as a test jellyfish. If it lives a month healthily, then you can feel safe in adding more jellyfish. If it dies, then obviously you need to make adjustments.
  • A spherical jellyfish tank kit can be purchased, with the link in the resources section, that includes everything you need, including the sponge filter..

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