moon jellyfish swimming

Spring Cleaning at the Aquarium

 After moving the hundreds of moon jellies to a back-up tank, 500 gallons of sea water are pumped out of the tank.  When the water level is too low for the pump, aquarists Gary Stoops and Ian Wallace resort to the old fashioned method of bailing the water with a scoop and bucket.Once a year, the Great Barrier Reef Aquarium crew takes on a daunting task:  draining, cleaning, and scrubbing the two 500-gallon jellyfish tanks.

“Once we have all the water out, we will scrub the tank walls to get rid of the old food, polyps, and debris that settle on the floor and walls of the tank,” Stoops explains. 

The moon jellies eat brine shrimp, and some of the unhatched brine shrimp eggs fall to the tank floor.  Polyps are the result of jellyfish reproduction, but these tiny jellies do not survive in the confines of the aquarium.

This spring cleaning event results in a major water change for the jellies, with about 80% of their tank water being removed and replaced (about 20% of the water is pumped into a sump, and will be added back to the tank).  For many aquatic species, this would present too much of a shock, but Stoops says, “Moon jellies are pretty hardy.” 

Stoops mixes up artificial sea water for the tank, which mimics the natural ocean in that it contains traces of nearly every element on earth.  Once the water cycles through the filtration system, it will be ready again for the moon jellies.

Click on the photos below to enlarge.