Was the pressure rising on your pump/filter while it was running? When was the last time it was backwashed? Why did you turn the pump off? Keep in mind that the chlorine killed the algae, but it's the filter that will remove it from the pool. If your pressure was rising on the filter, then you need to keep it running and backwash it as the pressure indicates. If the pressure was not rising, you can try adding a cupfull of DE through the skimmer to help coat the sand and help it pick up finer particles.