Done several jar tests last fall with samples of no Alum to high rates of Alum and any of the tests I done last fall, the sediment always went to bottom of container.
I pulled my first samples of the pond since the ice went off 6 days ago. We had some snow melt (slowly) on frozen ground and the pond came up a few feet but slowly, no bad run-off, for all practical purposes I would call it discolored like really weak tea. I have a 300' grass buffer that is mainly switch, western wheat and brome-very dense stand-about 3-5'tall and I'm hoping that discolor is "tanning" maybe??
The samples I pulled last night I brought home and put in qt size jars. I mixed differing amounts of Alum into several of these and the ones that cleared up the particulates are all at the TOP! dirty brown ring about 3/8-1/2" wide at the top??
Nothing at all on the bottom of jar like I had last fall, nothing.
I know you can get some floc at the surface but everything??
I could tell within 15 min there was a ring starting at the top. Today, big ring at the top and not anything visible on the bottom of the jars. Can anyone tell me what this means?

I suspect your floating ring is fine organic material that has washed in from your water shed.

Thanks Bill..So you're saying this is normal to have high amounts "surface" after an Alum treatment? Wonder how I can help eliminate that?? The entire area is grassed including the 2 sediment ponds it comes into first. neither has held water long enough to affect the growing grass. Maybe I have a grass that is not suitable for this purpose. I'm wondering if maybe making one of those into an artificial wetland marsh-type deal if that would help filter more organics out.. Humm.. More money..

Alum alone can lower pH enough to kill algae, which will gas up and float... Hydrated lime will do the same thing in a pond. Sometimes it looks like a really nasty, frothy, gunk....First mild rain will pop all the bubbles and it sinks.