The Copepod Connection | AlgaeBarn Aquarium Insights

Copepod Connection: Feeding, growth and Stability


Copepods are nature’s trophic intermediaries, meaning that they act as a link in the food chain by transferring nutrients and energy from lower levels like plants to higher levels like animals such as carnivores in the food chain. This makes them nearly indispensable in aquarium systems. They help in two big ways: (1) by eating unwanted material like nuisance algae and detritus, and (2) provide a natural food source for fish like anthias and mandarins, as well as corals. Even their young play an important role. Baby copepods feed on free-living, microalgae from the water column during their planktonic larval stages which helps keep the ecosystem balanced from the start of their life cycle.

Because they are more nutritious, pods prefer algal material over detritus. They mainly consume soft microalgae, meaning they do not graze on coralline algae or intact macroalgae (though they may consume decaying material). They thrive on green algae and diatoms, both available as benthic films for adults and planktonic single cells for larvae. A diverse copepod community helps keep water clear while reducing green and brown films from rocks, sand, and glass.

Since they’re so beneficial, aquarists often try to maintain large populations. However, pod numbers are limited by food availability. If added to combat algae or detritus, populations may initially rise during a growth phase but can decline once food supplies run low.

In some cases, populations crash before the algae or detritus is fully controlled or they never take off at all. Where mechanical filtration (filter socks, UV sterilization, etc.) isn’t the cause, the usual culprit is larval starvation. Remember, copepod larvae need phytoplankton. Aquarists who dose phyto regularly are able to keep stronger, more stable pod populations. Without phyto to support the babies, you won’t have many adults.

Phytoplankton is also key if you keep finicky fish such as mandarin dragonets or leopard wrasses that rely heavily on copepods for food. A single mandarin can consume thousands of pods per day, so keeping populations stable is essential. Even if you don’t keep picky feeders, striving for a balanced pod population is beneficial for any reef system.

The added bonus is that phytoplankton doesn’t just support copepods, it also nourishes corals directly and helps compete with nuisance algae by using up available nutrients. Together, phytoplankton and copepods create a healthier, more balanced ecosystem by feeding your fish and corals while naturally keeping the aquarium cleaner and more stable.