A natural habitat is an ecological or environmental area where a specific species lives. It is the place in nature that particular species calls home. To help picture what this means, think of a zoo.
Quick Answer. A mixture of vinegar and borax will kill most algae growing on bricks and concrete. Homeowners do not need harsh chemicals to get rid of these pesky growths.
The short version is - Algae is beneficial to fish the same way that plants are - they convert nitrate to a usable nitrogen source for consumption with the byproduct of oxygen. This oxygenates the water and removes harmful (to fish) nitrogen compounds.