A swimming pool is prey to contaminants like algae fouling the water. To get rid of the algae safely, use ammonia as the killing agent to raise the chlorine level of the water above 1 ppm (parts per million.) The ammonia will not stain the pool and is less expensive than using a metallic algicide. You can get the needed chemical at a pool or spa supply store or at home and garden shops.
Write down the total gallons of water in the pool -- this number can be acquired from the contractors who built the pool or in the user's manual. This number is necessary to purchase the correct amount of 2-lb. bags of quaternary ammonia.
Multiple every 10,000 gallons of water in the pool by 2 -- the number of pounds per bag of quaternary ammonia. Write down the total number of pounds you'll need.
Purchase bags of quaternary ammonia that equal the total pounds needed.
Put on a pair of work gloves. Pour a bag of the quaternary ammonia into a bucket. Add a quart of water into the bucket. Stir the mixture with a wooden paint stir for about a minute.
Stand at one end of the pool. Pour the mixture from the bucket into the pool as you walk around the perimeter. Continue doing this until the bucket is empty.
Refill the bucket in the same manner as in Step No. 4 and resume the procedure from the point where you stopped. Continue until all of the bags of the quaternary ammonia have been emptied into the swimming pool.
Return to the pool after 24 hours have passed. Vacuum the dead algae from the surface of the pool using a pool vacuum cleaner.