Aquarium Fish

Copepods: “Bugs” in a Reef Aquarium

posted: 05/15/12

Q. I have a 29-gallon reef aquarium with about 45 pounds of live rock and 30 pounds of live sand. The corals in the aquarium are primarily soft corals with a few hard corals. Recently, I've noticed a dramatic increase in the number of little white "bugs" all over the glass and rocks. What are these, and are they harmful to the other inhabitants of the aquarium?

A. The little white bugs you describe are actually small crustaceans called Copepods. Copepods themselves are not harmful, but the fact that their numbers have dramatically increased means there has been an increase in the crustaceans' food source, which includes algae, detritus, and decaying matter. These food sources could be in the form of an algae bloom, a large amount of uneaten food, or an organism that has perished and is decaying beneath the rocks.

The chance that the food source could be decaying matter in the aquarium indicates you should test your water for ammonia and nitrites (both are very toxic to your fish and live rock) and perform water changes, if necessary.

Copepods are a great food source for many species of fish and invertebrates. To control their numbers, consider getting some of the many fish that are natural predators of the Copepods. These include species of gobies, dragonets, wrasses, and pseudochromis.

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