I had a huge bloom in my tank. I had to shut off the lights for two days and I put in another K4. Sand was kind of fine for flow, so I aimed it towards the surface for agitation. My reasoning is that by increasing oxygen in the water I could combat the slime on two fronts.

I still have some minor stuff on top of my rock work... can't see any, but the tell-tale bubbles are visible at the end of the day.