Good question. Algae come in all kinds of shapes and sizes. Some algae, like the giant kelp that live off the coast of California, are 50 feet long.

Some algae are even too small to see. Many organisms live on the giant kelp. These organisms include fish, lobsters, shrimp, sea slugs, snails, crabs, other very small animals and many others.

Some organisms eat the giant kelp, like snails and sea urchins. In fact, groups of sea urchins have been known to eat whole kelp's forests. Many organisms eat the algae that is too small to see too. These organisms either filter them out of the water, like clams and worms, or they eat them off of rocks, like some snails and some fish. For example, some people like to have cleaner fish in their fish tanks to eat the small green algae, so the water doesn't get green.