algea

[help algae]

I have a sand filter and the pool is in ground. It is my mother's pool. It has algae and has been fighting it since May. When she went out of town I took a sample of the water to a pool store. they said to shock using 3 bags and aglae killer too. Of course run the filter for 24 hours. I have now done this three times and their is still green algae on the side of the pool. We brush the sides of the pool each day after adding the chemicals to the water. I no there is dead algea too. But I am really concern with the green patches on the sides of the pool. It is as if someone has painted certain spots of the pool with green algae paint. This cover about 1/4 of the pool's sides. The pool gets direct sunlight most of the day with little or no leaves to be found. We use well water. Does anyone have a suggestion.