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1816) species are hallmark "Pulse corals"
that are usually stalked, and sometimes branching,
with polyps restricted to the cap/crown (capitulum).
Xenia polyps may be long, will often
pulse, but are never retractile; their polyps
will contract (shrink), but never actually retract
into the cap/crown. The morphology and color
of Xenia species (and those still unproven
specimens that we call by a given species name)
is variable, but popular "types" include:
Xenia elongata (the common, brown "Fast-pulse"
Xenia), Xenia umbellata (white
"Pom-pom" Xenia), and an iridescent
blue-green species that strongly resembles X.
elongata (AKA "Silver-tip Xenia").
Hobbyists hold many more varieties in collections,
from nappy, yellow, Red Sea clusters to red-hued
Indonesian colonies, and numerous other members
of the genus found in colors ranging from cream
to green and through to dark brown. With perhaps
more than 60 species in this genus, Xenia
are widely distributed from the east coast of
Africa through to the central Pacific. They
are generally found in clear, bright, shallow
waters with moderate to strong water flow. Although
most Xenia are not common from turbid
or dirty waters, they will colonize early upon
stressed or damaged reef areas resulting from
pollution and natural disaster. A closer look
at their physiology reveals that Xenia
have weakly developed structures for organismal
feeding; nutrient uptake of dissolved matter
is conducted in this heavily photosynthetic
genus. Target feeding of Xeniids is not required
(if it's even practical or possible) to cultivate
them successfully in aquaria when there is an
adequate supply of nutrients available otherwise
(bio-load of fishes and other invertebrates,
most Xeniids are fast growing and may even be
considered invasive under certain circumstances.
It stands to reason that such successful species
are readily consumed by dedicated corallivores
and casual browsers of cnidarian tissue. Typically
"reef-safe" fishes like tangs will
often nibble Xeniids
and dubious characters
like angelfishes will often make a beeline straight
for a new colony placed in the tank! It's a
good idea to establish Xeniids separately, as
in refugia, up to several weeks in advance for
their safety before introducing them to the
main display. Since they do not feed significantly
on large solid matter/plankters, they are quite
safe to keep in a (coral) food-producing refugium
with little burden to the functional benefits
of the vessel. In fact, Xeniids are sometimes
used as "animal filters" much like
macroalgae with "vegetable filters"
for nutrient export because of their fast growth,
salability at harvest, and for their negligible
imposition on most other desirable life forms
For a more detailed
discussion of Xenia, see Anthony's feature
article in the February 2004 issue
of which this text is excerpted.
to Jonathan Bertoni (bertoni) for his assistance
on this project.
Reefkeeping Magazine Reef Central, LLC-Copyright © 2008