Green and yellow algae can be removed by super chlorination followed immediatly by brushing the pool walls and floor, vacuuming is recommended 2-4 hours later and then filter cleaning 24 hours later is a must to remove the algae spores from the flter elements. If you fail to clean the filter your algae will return.
To remove Black Algae it is advisable to use a product that is specifically designed for this purpose. The successful removal of Black Algae requires high free chlorine leves to be maintained over anextensive period of 3 -5 weeks and sometimes even longer.
In the winter months your pool can be kept free of algae by making sure you have a chlorine residual (free chlorine that is available to be used as a sanitizer) of 1 - 1.5ppm. In summer months increase that to 2.5 - 3ppm.
Of course, each pool reacts differently to its environment. Just because your pool is screened in and you have no trees directly overhanging does not mean that you will never get algae. Algae is airbourne. Good maintenance is the best way to ensure your pool remains algae free, weekly brushing of the pool walls releases contaminants that would otherwise encourage algae spores to flourish. Vacuuming weekly is essential to maintain analgae clear pool.
At some point pools will get algae, it does not mean that your pool water is unhealthy and unbalanced, increase the chlorine levels, brush, vacuum, clean and its gone.