Hi, and let me add my welcome!

You need to hold the chlorine level to 20 ppm until 1) the pool clears, 2)you are not losing more than 1 ppm of chlorine when measuring at night after the sun is off the pool, and again in the morning before the sun is on the pool. When both of those conditions are reached, then you can let your chlorine drift back down into the normal ranges for your pool, which are 5-10 ppm....from this point forward, you never want to let your chlorine get below 5 ppm, because doing so is an invitation for more algae problems. And no more trichlor for you!!

The blue water means it's clearing--the cloudiness is the dead algae, which will be removed by the filter. Just keep an eye on your filter pressure and backwash it as the pressure indicates. You can always add DE to the filter to help it along--you just want to add enough to raise your psi by 1 --and that rise may be slow, so add a handful or so, and then check it in 20-30 minutes. IF the pressure went up more than 1 psi, then you can always backwash it out and start over with a smaller amount of DE.

Janet