3 -4 days after the pool was closed Sept/07 I returned to the weekend house to find the filter still running. I turned it off and called the company that closed the pool. They said not to worry. I also mentioned the water level didn't seem low enough. They said not to worry. On 5/3 the pool was opened. It was completely green, almost black. The motor was frozen and had to be removed for possible repair/replacement. Could the pump motor be broken because the filter was left on running dry after they closed the pool? Does the water level have anything to do with a lot of algae? Could the algae have formed because they did put enough chemicals in before closing? How could the algae have been avoided?