The Cubic Aquarium Systems Orbit 20 is a purpose-built jellyfish aquarium kit designed for keeping moon jellyfish at home. It uses a kreisel-style circular flow to keep jellyfish suspended in the water column rather than getting sucked into a filter intake or settling on the bottom. The Orbit 20 holds 5.3 gallons and includes the tank, LED lighting with color control, a flow-through filtration system, and a small pump. For someone serious about keeping jellyfish at home, it is one of the better-designed options in this size range.

This article covers what the Orbit 20 includes, how the kreisel flow system works, what jellyfish it can hold, the setup process, common issues owners experience, and how it compares to alternatives at a similar price point.

What the Orbit 20 Kit Includes

The Orbit 20 comes as a complete kit with everything needed to start besides the jellyfish themselves and saltwater.

The kit includes:

  • The circular acrylic tank body (approximately 11.8 inches in diameter, 9.4 inches tall)
  • An external filter module with filtration media
  • An LED light ring with remote control (16 colors, brightness adjustment)
  • A submersible pump
  • Inlet and outlet fittings with fine mesh screens to protect jellyfish
  • Instruction manual

What you need to add: marine salt mix, a refractometer or hydrometer, and a quality marine salt like Instant Ocean or Reef Crystals to mix saltwater to approximately 1.023-1.025 salinity. You will also need RODI (reverse osmosis deionized) water or quality distilled water for mixing.

The kit does not include livestock. Moon jellyfish (Aurelia aurita) are the recommended species and the most commonly available for hobby keeping. Specialty suppliers like Jellyfish Art and Carolina Aquatics ship moon jellyfish nationally.

How the Kreisel Flow System Works

The defining feature of any jellyfish tank is the kreisel (German for "spinning top") water circulation system. Standard aquarium filters create suction and dead spots that are lethal to jellyfish, which are fragile animals with no real means of propulsion against a current.

A kreisel tank creates a circular, laminar flow that carries jellyfish gently around the tank in a continuous loop. The Orbit 20 achieves this through its circular tank shape and the position of the inlet and outlet ports. Water enters through a screened inlet on one side and exits through a screened outlet on the opposite side, creating a horizontal circular current around the tank.

The mesh screens on the inlet and outlet fittings are sized to prevent jellyfish from being drawn into the pump chamber. This is the most critical safety feature on any jellyfish tank, and the Orbit 20 handles it adequately for moon jellyfish. The mesh is fine enough to protect adult and juvenile moon jellyfish but requires cleaning every few days to prevent clogging, which reduces flow and can cause jellyfish to settle.

What Jellyfish Can the Orbit 20 Hold?

The 5.3-gallon volume sets practical limits on the number and size of jellyfish.

Moon Jellyfish (Aurelia aurita)

Moon jellyfish are the primary candidate. At adult size (3-4 inch bell diameter), the Orbit 20 is appropriate for two to three individuals. Keeping more than three adult moon jellyfish in a 5.3-gallon tank creates overcrowding and competes for the flow that keeps them suspended.

Smaller juvenile moon jellyfish with bells under 2 inches can be kept in slightly larger groups. Many hobbyists start with five to six juveniles, accept that some will not survive to adulthood (a normal loss rate for fragile invertebrates), and end up with two to three mature animals.

Lagoon Jellyfish and Blue Blubber Jellyfish

Lagoon jellyfish (Mastigias papua) and Australian blue blubber jellyfish (Catostylus mosaicus) are sometimes available from specialty suppliers. These species are more tolerant of variable water quality than moon jellyfish. However, both species can reach 10-12 inches at full adult size, making them unsuitable for the Orbit 20.

If you are interested in these species, a larger tank in the Cubic Aquarium Systems lineup, like the Pulse 80 (21 gallons) or Orbit 150 (39 gallons), is more appropriate.

For equipment designed for specific tank sizes, our best chiller for 20 gallon aquarium guide covers cooling options for small marine systems.

Setting Up the Orbit 20

Setup is manageable for someone with basic aquarium experience, though jellyfish keeping has some specific requirements that differ from standard fish keeping.

Cycling the Tank

New aquariums need to establish a nitrogen cycle before jellyfish are added. Jellyfish are sensitive to ammonia and nitrite, and even brief spikes during cycling can be fatal. Cycle the Orbit 20 with a source of ammonia (a few drops of Dr. Tim's Ammonium Chloride solution per gallon) and a bacterial supplement like Fritz TurboStart 900 for saltwater. Run the system for 2-4 weeks, testing ammonia and nitrite every few days. Add jellyfish only when ammonia and nitrite read zero and nitrate is detectable (confirming the cycle is complete).

Water Parameters

Moon jellyfish require:

  • Salinity: 1.023-1.025 specific gravity
  • Temperature: 68-77°F (20-25°C). Moon jellyfish are cold-water tolerant but do not thrive above 78°F for extended periods.
  • pH: 8.1-8.3
  • Ammonia: 0 ppm
  • Nitrite: 0 ppm
  • Nitrate: under 20 ppm

The Orbit 20 does not include a heater or chiller. In most room-temperature environments (68-75°F), this is adequate. If your home runs warmer than 77°F in summer, you will need a small aquarium chiller to maintain safe temperatures. This is a meaningful additional cost.

Feeding

Moon jellyfish eat live brine shrimp, frozen Artemia (brine shrimp), and specialty jellyfish food. Frozen Artemia thawed and strained is the most convenient daily food. Feed small portions twice daily, watching to ensure the jellyfish are capturing food rather than it accumulating on the tank bottom or getting pulled into the filter.

Common Issues with the Orbit 20

Owning the Orbit 20 comes with a learning curve. These are the problems owners encounter most often.

Jellyfish Settling on the Bottom

If jellyfish are sitting on the bottom rather than floating, the flow rate is too low. This usually means the mesh screens are clogged with detritus. Remove and clean the screens under running water. After cleaning, jellyfish should return to suspension within minutes if they are healthy.

If flow is adequate but jellyfish are still settling, check for internal parasites or poor health. Moon jellyfish that are underfed, stressed, or diseased lose the ability to maintain themselves in the water column.

Algae Growth on the Acrylic

Green algae grows on the interior walls of the Orbit 20 faster than in a typical reef tank because the LED light colors include green and blue spectra that favor algae growth. Clean the interior with a plastic scraper or soft cloth. Do not use metal scrapers on acrylic. A small cleanup crew of Mini Maxi Carpet Anemone cleaners is not practical in a jellyfish tank (they can sting jellyfish), so manual cleaning is the only option.

Pump Noise

Some owners report pump noise on the Orbit 20, particularly after several months of use. Calcium and salt creep can deposit on the impeller shaft, causing vibration. A monthly soak of the pump in a 50/50 vinegar-water solution keeps the impeller clean and running quietly.

How the Orbit 20 Compares to Alternatives

The jellyfish tank market is small but growing. A few alternatives worth comparing:

Jellyfish Art Cylinder Tank

Jellyfish Art sells their own cylindrical kreisel tanks in 3-gallon and 5-gallon sizes. The cylinder tanks are acrylic with a similar circular flow design. They are comparable to the Orbit 20 in capacity and function. The Jellyfish Art tanks come with a more comprehensive starter package including water conditioner and a cleaning brush, while the Orbit 20 has better LED control. Both run $150-200.

Desktop Kreisel Kits (Cubic Pulse 80)

If you plan to keep jellyfish long-term and want more flexibility on stocking, the Cubic Aquarium Systems Pulse 80 at 21 gallons is the meaningful step up. It accommodates larger moon jellyfish colonies, allows better water stability (larger volume buffers parameters more effectively), and can support some of the larger Pacific species that are inappropriate for the Orbit 20. Price runs $400-500.

See our best aquarium equipment guide for additional options across different tank sizes and applications.

FAQ

How many jellyfish can the Cubic Orbit 20 hold? Two to three adult moon jellyfish with bells at full adult size (3-4 inches in diameter). Smaller juveniles can be kept in slightly larger numbers, with five to six juveniles a reasonable starting point. Overcrowding stresses jellyfish and reduces the flow quality that keeps them suspended.

Do I need a chiller for the Cubic Orbit 20? If your room temperature stays between 68-76°F, no. Moon jellyfish tolerate this range well. If your home is warmer than 77-78°F for extended periods (common in summer), a small aquarium chiller is necessary. Prolonged temperatures above 78°F stress moon jellyfish and accelerate deterioration.

Where can I buy moon jellyfish for the Orbit 20? Jellyfish Art (jellyfish-art.com) is the most well-known US mail-order supplier. They ship live moon jellyfish in small quantities with heat or cold packs depending on season. Carolina Aquatics and some specialty marine fish stores also carry moon jellyfish periodically. Avoid buying jellyfish from general tropical fish stores that do not specialize in invertebrates, as care during shipping is critical and varies widely by seller.

How hard is it to keep jellyfish in the Orbit 20? Harder than keeping tropical fish, easier than keeping SPS coral. Jellyfish require stable water parameters, regular feeding, clean mesh screens, and careful attention to temperature. They are not low-maintenance pets. The most common cause of failure is poor water quality during the initial cycling period. If you cycle the tank properly before adding jellyfish and keep up with parameter testing, success rate improves significantly.

Summary

The Cubic Aquarium Systems Orbit 20 is a well-designed purpose-built jellyfish tank that handles the core challenge of jellyfish keeping, which is maintaining the circular flow that keeps these animals healthy. It is appropriate for two to three adult moon jellyfish and includes solid LED lighting with color control. The main gaps are the lack of an included heater or chiller and the need to manage mesh screen cleaning regularly to maintain adequate flow. For someone committed to jellyfish keeping at home, the Orbit 20 is a reasonable starting point in the $150-200 price range. If you want more flexibility or plan to keep jellyfish long-term, the Cubic Pulse 80 (21 gallons) is worth the additional investment.