This layer has many pores or openings. These pores or openings lead into tubes. Water can easily circulate through these tubes to all of the tiny animals. 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.