In the wild ocean, every rock is a
Like all cities, these rocks have
wonderful citizens; colorful sponges, interesting
corals and invertebrates. However, like cities, wild
rocks have their share of lowlifes, harmful creatures
that are difficult to remove. Wild rocks contain pest algae that resumes growth as soon as the conditions are right. I remember asking Sally Jo why her reefs did not have hair algae. She told me that if I did not want hair algae that I should not put any in my reefs.
One of these wild rock criminals is the notorious
mantis shrimp. We have no mantis shrimp at GARF,
because we use man-made aragocrete rock. Since we
don't see these mantis shrimp, we were all very
excited when a local hobbyist brought us a mantis
shrimp that he had found in his tank.
Our reactions to the shrimp were very
characteristic. Leonel, being practical, wanted to
kill it right away. Leroy wanted to create a whole
new aquarium for it, and I wanted to study it.
Mantis shrimps are crustaceans in the Order
Stomapoda. Genetically, they are rather primitive
cousins to many of the modern Decapods-shrimps crabs
Mantis shrimps can grow up to 30 cm in length but
start out as tiny creatures that burrow into holes in
rock. Small mantis shrimps embed themselves in rock,
and that is how they get into reef tanks: some
unsuspecting hobbyist buys live rock and ends up with
You may be thinking "what's so bad about mantis
shrimp?" Well, look at these claws:
This is just a baby mantis shrimp. Now, imagine those
claws enlarged to the size of a switchblade knife.
Mantis shrimp have a special nickname,
thumb-splitters. In a full-grown mantis shrimp, those
claws are entirely capable of delivering a nasty wound
to an aquarist who sticks his or her hand in the wrong
Of course, thumbs are not the only thing that mantis
shrimp will slice with their vicious claws. Mantis
shrimp are highly predatory, and can decimate
populations of fish and invertebrates. They lay in
wait, like our praying mantises on land, and simply
lash out at whatever prey is near. What a way for a
beloved pet fish to go- cut in half by the claws of a
I have had several frantic calls from people, whose
reef animals are being devoured by mantis shrimps. It
is not an easy matter to remove mantis shrimp from an
Their burrows are deep in the rock or sand
bed, and when they come out, they move quickly. An
aquarist with mantis shrimp can try to remove them
with tongs, spear them or trap them in some kind of
However, if a capture technique fails,
chances are it will never work. Mantis shrimp are
capable of learning, and they will be cautious the
As Leroy says, "You look at those eyes
and you know they are intelligent."
Often, the only
way to remove a mantis shrimp is to remove
every piece of rock until the mantis shrimp's home is
I'm very glad we don't have any of these creatures
living in the tanks at GARF. I'm also glad that I was
able to observe this fascinating, but menacing animal
in a safe way.
This is a special observation tank
that Leroy set up specifically for the mantis shrimp.
It's a simple ten gallon aquarium, placed in our
brood stock Palythoa tanks. Water pours down into it
from a tray above and is siphoned out, using some old
pipe and a soda bottle. This is how scientists set up
field aquariums. Leroy learned how to create these
during many field trips including two six week trips to Palau in 1979 and 1980 to study rare Chambered Nautilus with the help of the National Geographic society.
Eddie has made a lot of very nice aragocrete rocks.
These rocks are made of a porous, stable material and
have plenty of texture and space for corals to grow
and fish to hide. I guarantee, 100%, that our
aragocrete rocks are free of mantis shrimp.
EDDIE POSTMA'S NEWEST ARAGOCRETETM SCULPTURES
Using aragocrete rocks is one of the best things you
can do for your tank. They will not deplete the
ocean, or cause any environmental damage, and they are
Avoid the Thumb-splitters! Use aragocrete rock. On
sale at GARF for $5 dollars a pound
THESE ARAGOCRETE SCULPTURES ARE VERY LIGHT WEIGHT SO YOU GET LARGE ONES FOR LESS MONEY THAN
WILD ROCK THAT SHOULD BE LEFT ON THE REEF.