Water is very foamy

[Treebeard]

I treated with Chemiclean on Monday night, did a 20% water change on Wednesday night but the water returning to my sump foams instantly when it enters the sump. Forget about running the skimmer! I also painted the return in the display with black Krylon on Wednesday and let it dry for 24 hours before I put it back in the tank. I have used Chemiclean before but I do not remember it doing this to my water last time.