Helium.com | Ecology & Environment | The types of corals that form coral reefs http://www.helium.com/knowledge/233499-the-types-of-corals-that-form-coral-reefs.xml Helium.com > Ecology & Environment > The types of corals that form coral reefs en-us Copyright Helium.com Wed, 22 Apr 2009 20:43:22 GMT Wed, 22 Apr 2009 20:43:22 GMT What is a coral reef ecosystem? Introduction to coral reef ecosystem: Coral polyps are small marine animals that create limestone shells. These b... http://www.helium.com/items/1653775-coral-reef-ecosystem Thu, 19 Nov 2009 10:07:47