Spongilla lacustris can appear in several forms, including branching, clump-like, or crust. On average, the sponge grows to be a few inches in length. The color ranges from white to green, depending on the amount of zoochlorella, a green algal tissue, available. The algal tissue has a symbiotic relationship with the freshwater sponge. The algae help facilitate oxygen and food uptake for the sponge, while the sponge provides the algae a surface to live on.
