Nostoc and Anabaena are two different types of colonies that may sometimes be interchanged because of their similar features. One of the most noticeable differences that you will see is their shape. The Nostoc colony will have a way that is uniquely it's own. You will know immediately that it is Nostoc while the Anabaena is usually shapeless. If you are wondering where these two can be found, they are typically found in certain soils, in the bottom of lakes, some moist rocks, and so much more.
They are both unique because they have the power to perform photosynthesis, which used to be considered to be only done by plants. They have some pigments that they can apply for the process of photosynthesis.