How to Keep Jellyfish in Aquariums: An
Introductory Guide for Maintaining Healthy Jellies
Chad L. Widmer
Paperback, 5x8 in, 212 pages, Illustrated,
Bibliography
Wheatmark, August 2008
ISBN: 9781604941265
Endorsements
"Dude, this is gold!"
-- T. Knowles, jellies aquarist, Monterey
Bay Aquarium
"A great read; a must-have for anyone interested in keeping
jellyfish."
-- A. Pereyra, animal trainer, Monterey Bay
Aquarium
"I loved it! I feel very well informed, and I believe I could go
out and grow jellies right now if I wanted . . . Step-by-step
instructions were fantastic."
-- S. Wright, schoolteacher
Description
Many people want to learn how to keep and grow jellyfish in
aquariums, but don't know where to start. Though the
scientific literature contains clues, the language can be cryptic
for the uninitiated, and the references can be tricky to track down
without access to a well-stocked university library.
In this first-of-its-kind guide, Chad L. Widmer presents in
plain language some proven methods for jellyfish husbandry. With
some study, attention to detail, and a little pioneer spirit,
you'll soon be enjoying your own jellies, along with your
newfound jelly-keeping skills.
About the Author
Chad L. Widmer has managed display and culture of jellyfish
galleries at the Monterey Bay Aquarium, on Cannery Row in Monterey,
California, for over seven years. His scientific work focuses on
jellyfish life cycles and applied husbandry research and
development. After serving in the U.S. Army as an M-1 Abrams armor
crewman (an M-1 tanker), he earned his bachelor's and
master's degrees in marine biology from Humboldt State
University. He has been interviewed for a dozen different
television shows, including National Geographic Explorer and
Mythbusters.
Excerpt
Water Quality
Healthy captive jellyfish require excellent water quality.
Fortunately, one can use either natural or artificial seawater for
jelly keeping. I won't go into all of the details of how to
treat or make artificial seawater in this guide because there are
plenty of other resources available online and in other books. But
treat the water in your jelly habitat as you would treat a living
organism. Healthy jelly-system water should be well cared for, with
all the necessary elements in proper proportion, and maintained at
an appropriate temperature. Different jellyfish species have
different tolerances for seawater conditions ranging outside of
their normal operating conditions. Below I briefly discuss the
consequences of exceeding water quality parameters with commonly
kept jellies.
All jellies have an optimal temperature range in which they can
be maintained and remain healthy. When deciding on water
temperature, it is better to accidentally set the temperature too
low to start. If the temperature is too high for over forty-eight
hours, enzymes inside the jellies can get bent out of shape.
Affected jellies evert their bells (looking like a blown-out
umbrella in a wind storm) and have up to a 90% mortality rate. If
the temperature is too low, the enzymes are spared, but the
jellyfish pulse less, feed less, and metabolize food more slowly,
leading to slow or reversed growth. Fortunately, if you realize
that the temperature is too low, you can increase it by a few
degrees, and the jellyfish generally recover.
If you choose to collect your own seawater from the
ocean I highly recommend that when transporting your water home you
use tied-down recycled water jugs with secure lids for the trip. I
once used garbage pails with lids that weren't very secure to
transport seawater. I had painstakingly carried seawater-filled
buckets over sharp, jetty rocks while dodging waves at the Humboldt
Bay jetty. I arrived safely at my truck, but on the way home I took
a corner a little too sharply, accidentally spilling about 200
gallons and creating a mini-tsunami on the
freeway.
The average salinity of seawater used for growing most kinds of
jellyfish is about 33 parts per thousand (also known as practical
salinity units, or PSU). If the salinity in your jellyfish system
is too low, jellyfish may go downhill due to osmotic stress.
Species living in estuaries are far more tolerant of fluctuating
salinity than their open-ocean counterparts. Jellies that are
exposed to a high salinity and then returned to appropriate levels
generally recover. Therefore, it is important to monitor the
salinity levels in your system daily and make appropriate
adjustments. In lighted, warm-water life-support systems, water
tends to evaporate quickly, so it is often necessary to add fresh
water to make up for what is lost due to evaporation.
Keep track of your recipes for growing a
particularly good batch of jellies and try to duplicate and improve
upon them over time (e.g., "I kept a good group of Japanese
moon jellies at 34 ppt, 15°C, and fed them nauplii and small
krill . . .").
Comparatively speaking, jellyfish are more tolerant of lower
oxygen concentrations for extended periods than are fish. Having a
high tolerance for low oxygen concentrations is good news when
shipping jellyfish because they can get by with low oxygen in their
shipping bags for a few days at a time. Likewise, systems that are
supersaturated with oxygen tend to be bad for some jellies. Oxygen
can come out of solution inside the jellies' gut canals and
cause internal bubbles. Excessive oxygen can also be toxic to some
jellies, which is manifested as many small holes or pits on their
bells.
Keep track of important happenings in your jellyfish system. It
is a good idea to keep a log book next to the system in order to
record feeding times and amounts, performed maintenance, and water
quality parameters and times (e.g., salinity, temperature,
dissolved oxygen, date of last water change, etc.). A good log book
can help you unravel the mystery of why a cohort of jellyfish did
particularly well or poorly.
Basic Life-Support System Components to Consider
Life-support systems for jellyfish aquariums are similar to
life-support systems in most other aquaria. In the simplest jellies
system, there is a reservoir for holding water and a main jellies
display tank. An electric pump in the reservoir sends water to the
various components of the system much like the heart of a living
organism. Water is pumped from the reservoir to a chiller (if
required), which then returns water to the reservoir. Water is also
sent to the jellyfish display tank. After the water circulates
through the display tank, it returns to the reservoir after first
passing through a trickle filter and a bag filter. Protein skimmers
don't belong in your jellyfish system. There is growing
evidence supporting the idea that jellyfish can use dissolved
organic materials obtained directly from the water. A protein
skimmer may rob the jellyfish of food.
If water goes into a jellyfish tank, then water also has to
leave the tank. The general idea of water movement in jelly tanks
is to generate enough current to keep the jellies up and off the
bottom of the tank without having them get sucked out of the tank
as water leaves. Water leaves the display tank through an outflow
port (hole where water exits the tank); most outflow ports are
covered with some kind of screen mechanism to keep jellies from
leaving the display tank along with the water returning to the
reservoir. Several neat tricks have been developed to keep jellies
from sticking to the screens covering the drainage ports. Some of
the most common methods are laminar flow plates, spray bars, and
air bubbles. What these are and how they work are discussed in the
next chapter.
