What Do Copepods Feed On?

What Do Copepods Feed On?

Copepods are Nature’s trophic intermediaries. That is, they transfer nutrients and food energy from lower (e.g. plants) to higher (e.g. carnivores) levels in the food chain. This also happens to make them nearly indispensable in aquarium systems, where they (1) consume unwanted material such as nuisance algae and detritus and (2) are eaten by zooplanktivores ranging from fish (anthias, mandarins, etc.) to corals. Their young, quite notably, generally are phytoplanktivores, eating free-living microalgae from the water column during their planktonic larval stages.

As it is comparatively more nutritious, pods prefer algal material to detritus. They mainly consume soft microalgae. This means that they typically do not eat crustose forms such as coralline algae, nor do they eat macroalgae (aside from dead, decaying, softened material). They love green algae and diatoms; these are both available in a benthic form as thin films (for adult harpacticoid copepods) and in a planktonic form as single cells (for larval harpacticoid copepods and all cyclopoid copepods). As such, a diverse community of copepods helps to keep the aquarium water clear and the rocks, sand, and glass free of green or brown films.

Being so beneficial, aquarists generally seek to culture as high of numbers of these critters as possible. Unsurprisingly, their population densities are limited by food availability. This means that if you add pods to remedy a preexisting algae plague or detritus pool, you might observe steady increases during the exponential growth phase, only to see numbers drop as food supplies are gradually depleted.

Sometimes a pod population will decline before the nuisance algae and/or detritus is gone, or worse yet, they never really take off at all. Where losses to heavy mechanical filtration (e.g. filter socks) or
UV sterilization can be discounted, this usually due to the starvation of larvae. Remember, their “babies” need phyto! Those aquarists who dose phyto on a regular basis maintain larger pod populations (can’t have lots of adults without lots of larvae). And, when raised on a nutritionally balanced live phyto product such as OceanMagik, your pods will be more nutritious for the animals that prey on them!
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