August 1997

Q. I have a question about what occurred with my Brain Coral. I was
viewing the tank about a week ago, which is primarily a reef tank,
There are two brain corals in the tank, one on the right side, and a
much smaller one (that's not doing too well) on the left. The coral
on the right dilated in the center of it's right side. This hole was
approximately the size of the tip of your little finger. Once it was
dilated, it expelled a red substance that appeared to be stringy.
This substance was expelled in one large burst. The right side slowly
started to close up, and the left side started to dilated. While this
was occurring, the smaller brain coral on the left side of the tank
grew very large at the top portion. The coral on the right side then
began to dilate on the left side of the coral, and again expelled
matter into the tank, once this side was through, it closed as well.
There was no evidence of these enlargements in the coral after about
an hour.

After this occurred, the leather coral in the tank, had its nodules
enlarged. They then began to secrete a white stringy substance. This
coral then appeared to be weak, and withdrawn. It has finally
returned to it's original state.

I asked my local pet store about this. They are very knowledgeable
about salt water tanks, and he was puzzled. He said that he asked
several people and no one can verify what occurred. Can you explain
this? Could it be that the coral spawned? Is it possible for corals
to spawn in a controlled environment?

David Azura
via the Internet

David it is difficult to know exactly what happened in your tank. I
am not sure what genus of coral you are calling a "brain" coral but
by the description of one side opening up I assume you have what is
commonly referred to as open brain coral, Trachyphyllia
geoffroyi. As to what the red stringy substance was there are
three things that come to mind. It is possible that the red substance
was composed of excess zooxanthellae. At times corals will expel
zooxanthellae in long thin strands from their gastric cavities (see
photo on page 333 in volume one of The Reef Aquarium). Another
possibility is the stringy material may represent the expulsion of
detached mesenterial filaments from the coral's gastric cavity. Why
this might occur I have no idea, but it may be a stress reaction. The
third possibility is as you mentioned; reproduction. Given the
reaction of the leather coral, it is likely that what you witnessed
was spawning. If something like this occurs again try to obtain some
samples and examine them under a microscope if possible. This will
easily tell you if the string material is zooxanthellae, eggs, sperm
or something else.

Yes it is possible for corals to spawn in controlled environments
such as our aquaria. There is a long list of stony coral, soft coral,
anemone and gorgonian species that have been observed to do so. For a
complete discussion of reproduction in stony corals see volume one of
The Reef Aquarium and for sea anemones, soft corals,
gorgonians, zoanthids and corallimorpharians see volume two (which
should be available by the time you read this). Although many
aquarists can reproduce corals via fragmentation, sexual reproduction
offers a new challenge and it is only a matter of time till the
techniques used by scientists to spawn and raise corals will be used
by hobbyists to do the same in their own aquaria.

Q. I have a fifteen gallon mini-reef aquarium. There has been a recent
outbreak in a bristle-type worm. These worms are very small, (2-2.5
mm long and 1-2 mm wide. They are usually pink, or pink on the ends
and dark (almost black) in the middles. They have small
bristles-spines, no more than a half a mm long all over their body.
They reproduce very quickly; I can't remove them with tweezers fast
enough to deplete their population! In my aquarium, I have two blue
crocea clams, an open brain coral, many mushroom polyps, and a few
feather duster worms. How do I get rid of these bristle worms? Are
they dangerous to my clams? Is there a particular fish or shrimp that
will eat these worms, if in fact they are dangerous?

Steve J. Calvert,
California

These small worms are basically harmless and can actually be helpful
for a tank by feeding on and breaking down detritus. Moving through
the substrate they act like earthworms, loosening the substrate,
improving circulation while their metabolic activities contribute to
helpful bacterial populations. If their numbers increase greatly they
can become rather unsightly. It is possible that large numbers of
these small worms can irritate the clams if they get between the
valves and the mantle or between the substrate and the byssal opening
of the clam.

Removal is relatively simple. In a tank as small as yours you could
easily siphon the substrate out and rinse out the worms. You can also
place pieces of shrimp inside a section of nylon stocking and place
this in the tank. The worms will swarm over the bait and their
bristles will become entangled in the nylon mesh. It is then a simple
matter to remove the stocking and rinse off the worms. Several fish
will feed on these worms such as pseudochromids (dottybacks) and
small wrasses.

Q. I found a biological company in the Carolina's that will sell live
marine rotifers. I will use these rotifers to feed the fry of my
marine clownfish. My question is, do I keep the rotifers producing
themselves by simply keeping them in saltwater with the same
conditions of the clownfish tank water. Can I freeze the rotifers,
like they freeze live foods, and keep it in a freezer until I need to
use them? Any info you could give me on this topic will be greatly
appreciated.

John Durante
Long Island, N.Y

John, rotifers will do just fine in the same water as your clownfish.
However, they need to be fed or else they will quickly die. If you
can get a steady supply of well-fed rotifers (i.e. every day) then
there is no need to feed them. You will need to find out if the
rotifers you can acquire are nutritionally enhanced. If not then you
will have to culture them in a separate vessel and keep them
well-fed. Common foods you can use for the rotifers include
microalgae, or yeast. I should point out that yeast fed rotifers are
much lower in nutritional value than those fed microalgae and yield
poorer results when used to raise larval fish. There are a few
commercial preparations available that you can use to not only feed
your rotifers but also culture new ones, contact Florida Aqua Farms
Inc., 5532 Old Saint Joe Rd., Dade City, FL, 33525. This company
sells "resting" rotifers (a dormant stage), as well as microalgal
cultures and additives to enhance rotifer colony growth.

Freezing the rotifers is not a good idea for a couple of reasons.
Freezing and storage tends to degrade the nutritional value of the
rotifers. More importantly freezing will kill the rotifers and dead
rotifers don't swim too well and therefore do not illicit much of a
feeding response in larval clownfish. Although some success can be
had by feeding prepared foods to larval clownfish, so far only live
foods give good survival rates. For additional information on rotifer
culture I would recommend that you get a copy of Martin Moe's The
Marine Aquarium Handbook: Beginner to Breeder, published by Green
Turtle Publ. or The Plankton Culture Manual by Frank Hoff and
Terry Snell, published by Florida Aqua Farms, both of which give
detailed instructions on growing rotifers and their microalgae food.