How Do I Know if I Have Copepods in My Tank?

Calanoid copepods are tiny creatures, often less than one eight of an inch long. These minute invertebrates have elongated bodies and frilly appendages, including long antennae. Copepods are able to swim and remain in the water column at all times. Harpacticoid copepods are smaller than calanoid types and spend most of their time just above the rocks and gravel. They frequently crawl along the glass panes, in search for algae. Harpacticoid copepods are torpedo-shaped and their antennae are much shorted than those of the calanoid group. Although extremely small, both types of copepods can be found, if the aquarist looks carefully enough.

Things You'll Need

  • Marine aquarium, with strong overhead lights
  • Live rocks
  • Magnifying glass
  • Bathroom taps
  • Plastic jug
  • 5-gallon bucket
  • Flashlight
  • Mandarin dragonets or scooter blennies
  • Sump
  • Refugium
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Instructions

    • 1

      Turn on the aquarium lights to assist you in finding the copepods.

    • 2

      Use a magnifying glass to look very closely at the live rocks and substrate in the aquarium. Examine any encrusting algae growths in particular and look at the growth and in the water directly above the algae. Copepods spend much of the day grazing on this type of algae, but often travel just above the rocks and substrate.

    • 3

      Rinse your hands under hot running water to remove traces of household soaps, detergents and body creams, as these are detrimental to salt water and the creatures that live in your aquarium.

    • 4

      Use a plastic jug to add aquarium water to a 5-gallon bucket. Remove a piece of live rock from the aquarium and shake it in the bucket. Live rock is not alive as such, but has a huge number of living organisms growing and living on the rock.

    • 5

      Return the live rock to your aquarium.

    • 6

      Take the bucket into strong sunlight or use a flashlight to examine the bottom and inside walls. Copepods, which were hiding in crevasses in the rock, will have been shaken into the bucket, where it is easier to see them.

    • 7

      Closely observe the feeding behavior of any mandarin dragonets or scooter blennies in the aquarium. Both of these fish species feed on copepods and you will see them picking at the glass and at rocks as they find and eat the copepods.

    • 8

      Use a magnifying glass to closely examine both the glass and substrate in the refugium compartment of your sump, for signs of copepods. Sumps are glass aquariums that are positioned below the main aquarium and attached to the aquarium via piping. The refugium is a compartment within the sump, used to grow algae and tiny food organisms such as copepods.