Statoblasts, which allow such moss animals to reproduce asexually, are clearly visible in these
bryozoans growing in an aquarium.
Dragonflies and damselflies are from the
insect order Odonata, and they were flying
around the earth before the dinosaurs
ruled. We recognize these interesting and
beautiful creatures from their final adult
flying stage, but most of their lives are
spent in the water in a larval stage.
The larvae can come in on plants or
anything collected in water outdoors.
The larval stage usually lasts from one
to two years. Both larvae and adults are
predacious and are happy to eat not only
other invertebrates, but also fish. They are
very good at camouflage—if one sneaks
into your aquarium and it’s heavily planted,
you may never even notice that it’s there
until you see it flying around your home.
Dragonflies generally look larger than
the slender-bodied damselfly, even in larval
form. Dragonflies have a rear pair of wings
that is larger than the front pair, while
both pairs are the same size in damselflies.
Damselflies can, however, fold their wings
behind their backs, an ability that the other
lacks. Damselflies also have three featherlike tails, which function as external gills.
There are thousands of other freshwater
invertebrates that can be introduced into
the aquarium. Most of them are quite small
and some can be a nuisance, but there are
also many that are attractive, interesting,
and able to thrive in an aquarium. In fact,
there seems to be more of an interest in
freshwater invertebrates lately, certainly in
snails and shrimp, and I see more people
posting Websites and experiences with
other freshwater invertebrates as well.
Looking back at all the advances made
in aquarium keeping over the course of
my lifetime (and also considering how
much faster advances have been made
since the popularity of email and Webpages
has grown) makes me believe that more
freshwater invertebrates will become
available in the next several years.
I can certainly see the star of a 10-gallon
aquarium being a large predacious diving
beetle hunting down live prey, or even an
underwater scorpion—a walking stick that
sucks the bodily juices out of its victim
like a vampire, leaving a limp carcass to
In the course of your planted-aquarium hobby,
you may run into some unexpected invaders
that hitch a ride in with your plants. Most of
these animals are harmless and some even make
great fish food, while populations of others could
indicate possible problems in your aquarium. Still
others happen to be voracious hunters that can eat
fry or fish—which, depending on your point of
view, may or may not be a good thing. D