Oyster as Filters


  • Oysters act as a natural filter for the Bay, as they filter the water for their food.
  • Dirt, nutrients, andalgae can cause problems in Bay watrs. Oysters filter these things, and either eat them or shape them into small packets, which are deposited on the bottom where they are not harmful.
  • The oysters in the Bay could once filter thenetire body of water in three to six days. With the decline of the number of oysters now in the Bay this job would now take the oysters almost a year.

Activity: Oyster Filter


  • one aquarium
  • Four to six live oysters
  • Water
  • Sea salt
  • Algae, fine dirt (or pond water if available)


  • Mix water with sea salt to 12 parts per thousand (ppt) See Maryland Anatomy Web site for more explicit directions for longer term culturing of the oysters.
  • Pour the cloudy water into the aquarium.
  • Students now will write their observations regarding the appearance of the aquarium.
  • Place the oysters in the tank.
  • Have students record the time.
  • Students will record observations every 20 minutes in their science journal.

As the oysters filter the water for food, the clarity will improve. At the end of two hours water will be clear.

 Return to Oyster page