appearance. In fact, planaria are even in
a class of flatworms called Turbellaria.
Planaria I’ve seen in the aquarium have
been in shades of white, brown, or green,
but other colors can occur, some of which
have patterns. Planaria often have a headlike area that is somewhat arrowhead-shaped, coupled with eye spots. The eye
spots are light-receptive, but they are not
Planaria glide across surfaces in the
aquarium, and they generally eat much
smaller animals that live on those surfaces.
Some species of planaria will even ingest
hydra and store the hydra’s nematocysts
for their own future defense. They may
also feed on fish eggs.
Planaria are not uncommon in the
aquarium, but having large populations
of them usually means that the aquarium
is experiencing some pollution issues.
Overfeeding, overcrowding, inadequate
filtration, and insufficient water
changes can all contribute to these
types of infestations.
Hydra will attach to any surface in the aquarium, including a plant leaf such as this one, where they
will wait to catch a meal.
Just the idea of leeches often gives
most people a case of the heebie-jeebies.
Though a few leeches feed on mammals,
most prefer a cold-blooded meal, while
a few are scavengers, and still others eat
plants. Leeches are usually introduced
through plants or live foods that come
from natural sources or ponds. I’ve also
even seen wild-caught fish that have had
Leeches differ from planaria in that
they are segmented and have suckers at
both ends. This gives them the ability to
move like an inchworm through surfaces
in the water. Leeches are variable in color,
but the ones I’ve seen on fish or in the
aquarium have been a plain light tan or
brown. The ones I’ve had the displeasure
of being bitten by while collecting have
I haven’t had much experience with
leeches on my own fish, but I have seen
them in store tanks, on wild-caught fish,
hitchhiking on things I’ve collected, or
on things from someone’s pond that have
been placed in quarantine tanks. For
leeches that are infecting fish, the most
recommended remedy is a saltwater bath
for the fish. There are also medications
available in most pet stores that may
help for more severe problems. Since
different species of fish have different
tolerances for both salt and medications,
you should research your specific fish
before treatment. The Internet and books
are good places to start.
I should also mention that some
people have aquariums specifically for
keeping leeches. Some leeches can get
quite large, and many have interesting
colors or patterns.
Mosquitoes rarely show up in waters that
have fish in them, but will very often show
up—as if by magic—in almost any water
situated in warm weather. This certainly
includes any aquarium that has no fish in
it, the water left in a saucer of a house plant,
or any container that might have water in
it that is located outside. Mosquito larvae
can show up almost anywhere there is still
or slow-moving water.
Both male and female mosquitoes ingest
nectar, but females need blood to lay their
eggs. Different species of mosquitoes like
to feed from different species of animals,
including, of course, humans. So after
feeding off of you, a family member,
or a guest, the female mosquito finds
water in which to lay her eggs. They
can lay up to 200 eggs in little floating
groups called rafts. The eggs generally
hatch in the next few days, depending
Though this animal has eye spots like a
planaria, it’s actually a leech, with suckers on
on conditions, and then go through four
larval stages. They hang head-down at the
water surface, breathing through a siphon
tube. In about one to two weeks the larvae
turn into pupae. They can still move when
disturbed, but not as well as when in their
larval form. The pupae have no mouths,
so they cannot eat, and they look like
large commas hanging in the water. They
emerge from this stage in just a few days
as full-fledged adult mosquitoes.
The best way to get rid of mosquito
larvae in an aquarium is to add a fish.
There are very few aquarium fish that
won’t be delighted to eat mosquito larvae.
Shrimp seem to love them too, if they can
catch them (and they usually can).