yep all algae is, is a plant that filters excess nutrients, gunk, nitrates out and put oxygen into the water. caulerpa can be troublesome because it will release the nutrients it has aborbed if it 'goes sexual' or dies off. experienced algae keepers view this as more of a responsibilty or a neusance than a threat. i think your red one is not caulerpa but i would ask someone about your green one.