These individual animals make up the living jelly-like cells of the sponge. They feed by filtering microscopic plants and animals from the water. Freshwater sponges are much smaller than the average saltwater sponge. The colonies are usually about 2.4 cm across. Some colonies form a carpet over a metre across.
Sponges grow on rocks, but more commonly on submerged sticks and branches.
They usually look like soft blobs of old foam cushion. In colour, they are a dull creamy brown to medium brown. Many colonies take on a green colour because they contain algae. The algae are trapped in the pockets or pores that go all through the sponge. To keep the sponges from collapsing, sponge animals produce rod-like 'spicules' or pillars of silica.