You can put the polyquat in, if you want--but I would wait until you clear up the algae, if that's what it is....polyquat will create a chlorine demand, and you need all the chlorine working that you can get, right now.

The easiest way to tell if it's algae or not is to test your chlorine levels (free and combined) at night after the sun is off the pool, and then test them again in the morning before the sun is on the pool. If you didn't lose any chlorine overnight, then you don't have algae. If you lost more than 1 ppm of chlorine, and/or if your CC is 1.0 or greater, then you have something, most likely algae, in the water.