I have always wondered if there are such animals as freshwater corals-are there coral reefs in tropical lakes? How about spoanges? What is freshwater coral like-is it as colorful as the saltwater variety?
Looks like coral is exclusively marine.http://www.encyclopedia.com/html/c1/coral.asp
Sponges, however…http://www.encyclopedia.com/html/s1/sponge.asp
sponge
common name for members of the aquatic animal phylum Porifera , and for the dried, processed skeletons of certain species used to hold water. Over 4,500 living species are known; they are found throughout the world, especially in shallow temperate waters. All are marine except the members of a single freshwater family.
Freshwater sponges.http://bioweb.uwlax.edu/zoolab/Table_of_Contents/Lab-3a/Freshwater_Sponges/freshwater_sponges.htm
In addition to containing many marine forms, the Class Demospongiae also contains about 150 species of freshwater sponges. Most of these species lack any distinct symmetry and grow as encrusting organisms on hard substrates such as rocks, sticks, etc. Conditions within such habitats can be far more variable than those experienced by sponges living in marine environments, and during the onset of unfavorable periods (freezing, drying, etc.), freshwater sponges undergo asexual reproduction to produce internal buds called gemmules. Although the parental sponge may die and disintegrate, the gemmules are highly resistant to adverse conditions and will develop into new sponges when conditions improve.