Amphipods Vs. Copepods: What’s the Difference?

Arturo Alvarez-Demalde

Arturo Alvarez-Demalde

As I’ve previously shared, I’ve always had a fascination with marine life. I like to spend as much as my time out at sea and when I have to be on land, I retreat to my large collection of saltwater reef aquariums. Today I discuss amphipods and copepods.

Amphipods and copepods are marine creatures that are essential components of any healthy aquarium environment. Because of their small size, and the fact that they share a suffix, these tiny creatures are often lumped together into one group by hobbyists and novices. There are a few easy differences between the two species that can help even the most inexperienced aquarium tender identify and classify each one they see.

Amphipods are small crustaceans of the group ‘Amphipoda’. They are flat little creatures that feature multiple appendages, including antennae, gnarthopods and thoracic legs. Hobbyists often compare the classic appearance of an amphipod to that of a grasshopper, or even a floating comma — this distinctive bent shape can be recognized and noticed from a fair distance due to the not-insignificant size of amphipods. They often act as a handy food source for larger fish in aquarium tanks, and they can flourish if provided rock nooks and crannies to hide and breed in.

Copepods, on the other hand, are absolutely tiny — they are very difficult to see unless a large group of them masses together in the tank. These minuscule crustaceans are present in most marine environments, and although many members of the ‘Copepoda’ group are parasitic, copepods are mostly free-living. Copepods form an essential link in the marine food web: they graze on phytoplankton and detritus, and incorporate the fatty acids and proteins from these foods into their bodies. They then serve as a primary source of food for many aquatic animals. In fact, the fatty acids and omega acids that are extolled by fish-loving dietitians mostly are derived from consumption of copepods.

Copepods and amphipods often share the same aquatic spaces, but they rarely interact and are not even part of the same segment of the crustacean family. Generally, if you can see a small crustacean in your aquarium from a distance of greater than ten feet, it is an amphipod.

In order to maintain a healthy aquarium, both of these tiny creatures should be aggressively cultivated and given a chance to thrive. Specialists and experts like those at Aquarium Depot can give new owners advice on how to treat, feed, and interact with these crustaceans. Visit any location today, or contact Aquarium Depot to talk with a copepod and amphipod expert. These little guys can improve the quality of your aquarium, but you are responsible for ensuring their continued survival!


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