Copepods are good. The more, the better. That’s why you want
to produce as many as possible. And as fast as you culture them, your corals
and small reef fish will eat them! For sure, due to the heavy predation that
typically occurs in a reef tank (a single mandarin can eat hundreds of adult
copepods every single day!), you will have to make some effort to maintain
large pod populations.
Maintaining consistently high copepod densities requires (1)
constantly replenishing the population with fresh stock from outside the tank
(i.e. regularly buying them) or (2) building and sustaining a large, stable
population inside the system. For most aquarists, the second option is
preferable as (1) it is less expensive over time and (2) there is an
uninterrupted food supply for the species that depend upon them. In many cases,
it is necessary to bolster the population with a bag or two of new pods from
time to time. But one can keep a pretty reliable availability of pods present
at all times when using a refugium.
The most wonderful thing about copepods is that (at least as
adults) they survive by eating unwanted stuff like film algae and detritus. As
such, they may be the most important members of your clean-up crew! However,
the juveniles have significantly different eating habits. This is because they
live a planktonic lifestyle during the larval stages (yes, even the
harpacticoids which live on the bottom as adults). It’s important to remember
that even though you’ll see the adults concentrated in the fuge, the
microscopic larvae are freely drifting everywhere! While living in the
plankton, and developing rapidly, they consume phytoplankton.
Some phyto is naturally produced in your tank, but is
rapidly consumed by corals, clams, etc. or is removed/killed by the filter
system, sterilizer, etc. Thus, in order to support naturally high populations
of young pods (as well as keep your corals, clams, etc. well nourished), it is advisable
to regularly dose live phyto. In supporting a large population of copepod
larvae, you’ll always have a sure supply of big, fat, healthy adult copepods!