The Care and Feeding of Mushroom Anemones
(Suborder: Corallimorpharia)
by J. Charles Delbeek M.Sc.

Mushroom anemones are closely related to the stony corals and belong
to the same order: Scleractinia (see Table 1 for a complete
classification). There are approximately ten families of mushroom
anemones found in most of the tropical oceans of the world, however,
the majority of those imported for aquariums belong to the family
Actinodiscus;  sometimes  we also come across large individuals
(Elephant-ear anemones) which belong to the families Ricordia and
Rhodactis (Achterkamp, 1985). Mushroom anemones can be found as
individuals but are more common in colonies. Even though they exist
as individual specimens, they are often joined to each other at their
basal discs (Achterkamp, 1985).

In nature, mushroom anemones are usually found in areas of poorer
water quality and clarity than stony corals. Perhaps that is why
mushroom anemones are relatively easy to keep and breed in the home
aquarium compared to the more delicate hard corals (Achterkamp, 1985).

Feeding
As in the case of reef building corals, giant clams of the family
Tridacnidae and most sea anemones, mushroom anemones depend to a
great extent (some more than others, as we shall see) on symbiotic
algae, zooxanthellae, for their existence (Gordon, 1977). These
zooxanthellae live in the tissues of their host and convert the
energy of the sun, via photosynthesis, into a form which the host can
use. In return, the zooxanthellae feed on the ammonia produced by the
host (for more on zooxanthellae, see the article in this issue). Some
hosts can do quite


Table 1. Classification of mushroom anemones (Achterkamp, 1985; Barnes, 1974).


Phylum:  Cnidaria           - free-swimming and sessile with stinging
                              tentacles surrounding the mouth

Class:  Anthozoa            - sea anemones and corals

Subclass: Hexacorallia      - polyps with more than eight tentacles

Order:  Scleractinia        - stony corals

Suborder: Corallimorpharia  - tentacles radially arranged around the
                              mouth
                            - resemble true corals but lack skeletons



well without their zooxanthellae, however, mushroom anemones are not
among these; if their algae die, they will soon follow! If their
zooxanthellae die, some mushroom anemones will not be able take in
food from outside (Achterkamp, 1985). As was mentioned earlier, some
mushroom anemones are more dependent on zooxanthellae than others. A
good indication of this is the texture of their upper surface. If the
surface is relatively smooth, with few knob-like tentacles, then one
can assume that this type depends mostly on zooxanthellae. Those
mushroom anemones with a rougher surface are more likely to accept
additional food (Achterkamp, 1985). One way to determine if your
mushroom anemone requires food is described by Achterkamp (1985). If
you stroke the sides of the anemone with a piece of rigid tubing, and
it folds into a shape reminiscent of a tulip bulb (this may take a
few minutes), then this is a good indication that your mushroom
anemone will accept additional food. If you put some food into the
cavity formed when the anemone takes on the "tulip" shape (mysis
shrimps or other small food types). When it reopens, the cavity will
be empty, indicating that the food has been eaten. The larger
mushroom anemones, belonging to the family Rhodactis, have numerous
bumps on their surface,are predatory in nature and will prey upon
small fish (now you know where that goby went!).

Mushroom Anemones in the Aquarium
The majority of mushroom anemones are brown in colour, due to the
presence of zooxanthellae (which are brown algae, not green). In some
cases you will come across individuals which are almost white in
colour. This is almost always an indication that the zooxanthella
have died off and the anemone is in poor condition (i.e. don't buy
it!). This is often the result of lack of light over a long period
(such as occurs during long shipping periods) or they were shipped
with too much oxygen in the bag (Achterkamp, 1985).

Although zooxanthellae need a lot of light, at times they can receive
too much light. For example, even though mercury-iodide lamps are
good for leather corals, they are too bright for mushroom anemones,
therefore they should be placed deeper in the aquarium or in a shaded
spot (Achterkamp, 1985). In nature, mushroom anemones which live in
areas of strong light develop a pigment layer to absorb the extra
light. This results in a variety of coloured individuals (e.g. blue
and red). However, if these types do not receive enough light they
will rapidly loose this protective colouring. Therefore, many of the
coloured mushroom anemones that are imported have lost their pigment
due to the long period they have spent without light. The trick is to
get ones which have spent the least amount of time in transit. If you
trust your dealer, you can buy those brown ones he says were once
blue and, provided you give them enough light, they will regain their
brilliant colouring (in a few months) (Achterkamp, 1985).

When placing your mushroom anemone in the aquarium there are a few
points you should consider:

1. If you have normal fluorescent lighting, place them as close to
the surface as possible to receive as much light as possible. You can
tell how your specimens are reacting to the light by the shape they
assume. Normally, mushroom anemones lie perfectly flat against the
substrate. If they take on a trumpet shape in the mid-  afternoon, or
for the whole day, they are not receiving enough light or light which
is too red (Achterkamp, 1985).

2. Do not place your colony near the outlet of the water pump. In
contrast to leather corals, mushroom anemones do not like a lot of
current. If you have a well-lit aquarium, you can place them lower in
the tank where they will not be subjected to strong currents
(Achterkamp, 1985).

3. Keep your mushroom anemones well away from strong stinging animals
such as bubblecorals and Cerianthus anemones (Achterkamp, 1985).

4. Mushroom anemones will start to suffer at nitrate concentrations
greater than 30-40 ppm.

5. Mushroom anemones may require several weeks before they become
completely accustomed to your tank, especially if they have just been
imported, so don't worry if your newly acquired colony looks like a
pile of dead leaves at first. They will soon regain their former
glory (Achterkamp, 1985).

Reproduction
Like most anthozoans, mushroom anemones have strong powers of
regeneration. The are reported cases of mushroom anemones being cut
in halve, and each half then regenerating itself (Achterkamp, 1985).
Mushroom anemones reproduce by splitting in two or by budding off
small individuals from the pedal base; these small individuals then
grow rapidly. In an aquarium with good water quality, mushroom
anemones can reproduce themselves five-fold within a year
(Achterkamp, 1985).

When the colony becomes too crowded, individuals will let go of the
substrate and float to a new area and reattach themselves. Unlike sea
anemones, this process (reattachment) may take a few weeks. Whatever
happens, don't try to remove an individual yourself; this always goes
awry (Achterkamp, 1985).

In conclusion, mushroom anemones are excellent choices for the
aquarium with good water quality. They can be kept successfully by
beginner and expert alike (Achterkamp, 1985)!

References
Achterkamp, A. 1985. Schijfanemonen In. Gids en handboek voor de
zeeaquariumliefhebber en amateur zee-bioloog. (A.P. Amir and  H.
Compaan ed.), Nederlandse Bond van  Zee- aquariumverenigingen,
Vroomshoop, Nederland.

Barnes, R.D. 1974. Invertebrate Zoology. W.B. Saunders Co., Toronto.

Gordon, M.S. 1977. Animal Physiology. Macmillian Publishing Co., N.Y.