Lots and lots and lots of chlorine (use Bleach or LC). Keep it at shock levels. Run your filter 24/7, and, if you don't have them, get and use skimmer socks. I find I can use one for a month before I have to replace it, so that's about $5 for skimmer socks for the summer.

You can probably use your hand skimmer to lift the foam off as much as you can.

You learned the hard way why the ONLY algaecide we recommend in Polyquat 60%--it never foams. It's only side effect is to drop FC if you use a lot of it.