Keep the level of chlorine at 15 ppm until you can test at night after the sun is off the pool and again in the morning before the sun hits it, and lose less than 1 ppm. Then keep it high for another day just to be on the safe side (assuming you can no longer brush up anything green) and then you can let it start to drift back down. I wouldn't use a clarifier just yet--the chlorine killed the algae, but your filter has to have a chance to filter it out of the water. We generally recommend brushing daily, and watching the pressure on your pump and backwashing when you get to 8-10 psi over "clean pressure". AFter a few days you should begin to see it clearing. If not, then you can try shutting the pump off and letting it all settle to the bottom to be vac'd out.