Many plants use nitrates for food, and in this case, low nitrate levels can actually cause problems and can even lead to a blue-green algae (cyanobacteria) outbreak. How do you test for nitrates? To identify the nitrate levels in your aquarium, all you need to do is go out and buy a...
but they lack many of the distinct organs that you will find in a higher plant. The higher plants are believed to have evolved from algae, and algae are believed to have gotten their capacity for photosynthesis from cyanobacteria.