Are Copepods a Good Sign?

Copepods are widely believed to constitute over 75% of the
biomass of all zooplankton on Earth. They may be found in nearly every marine
and freshwater habitat from coral reefs to roadside ditches. But it is not just
their omnipresence that makes them so important ecologically; because these
tiny herbivores/detritivores pass nutrients and energy from lower to higher
levels of the food chain, they serve as vital trophic intermediaries.

Still, like any organism, their populations are limited by
the availability of food (among other things). Where there is abundant food
available to them, copepods may proliferate to reach unbelievably high
densities. Tigriopus, for example, can form lasting populations of over
800 individuals per liter; it can reach densities of 20,000 individuals per
liter where conditions are cozy and food is plentiful.

Let’s just get this straight: Copepods are always a good
thing to have in an aquarium. First, they do absolutely no harm. In fact,
because their favorite food is stuff like suspended particulate matter,
detritus and film algae, they add punch to your clean-up crew. They are also an
excellent, natural, nutritious food source for corals and small reef fish.

Indeed, more and more aquarists are making a habit of
introducing (and even periodically replenishing) copepods as part of their
regular maintenance/feeding regimen. Even so, you might pick up one or two
species as hitchhikers on pieces of live rock, coral frags, etc. Many aquarists
first notice copepods as miniscule “bugs” crawling over the glass of the tank

A few such incidental pods are great… a nice freebie,
really. Over time, under normal circumstances, their population will stabilize.
At this point, you’ll notice a few here, a few there… but they’ll probably
never really reach huge numbers due to factors such as predation. You however might have very large numbers of pods if your system is full of detritus or algae--but
that doesn’t make the pods bad; in fact, be glad that they’re there, because
they’ll be your first line of attack against organic wastes and unwanted