I drained my contact tank today (I treat with Hydrogen Peroxide). I didn't see much solids when I started draining. I typically don't see much. But check what came out after I was done draining the tank and moving it around. Treated water moves from the bottom of the tank to the top. If this stuff was suspended or floating, why doesn't it leave the tank? I put a handful of it in clean water, and some floated, some suspended, and some sank. I picked up about 3 gallons of this stuff. I will post some additional pictures. I'm curious if anyone has seen this stuff before. We get a bit of pink in the back of our toilets and at the liquid level in the toilet bowl. However, I never seen nodules. I wish I had checked the H2O2 levels before I drained. I speculate I'm running 10 to 30 ppm H2O2 in this tank. Whatever this is, doesn't mind H2O2.