So I'm getting ready to do alum treatment this week on my newer ⅕ acre pond (two years old, stocked with LMB, BG, HBG, RES, CC fingerlings and a single koi in april), the fish are doing great with high daily feeding activity. Was just treated with soilfloc a week a ago to stop a seep in the spillway. The pond itself was built by damming off a pair semi-ephimeral steams where they converged with 15ish acre forest/brush/ and cattle pasture watershed feeding it . I've pulled 2 common snappers out of it already and know there is at least one more in there but its sub three inches and thus can escape the turtle trap I bought. After a heavy rain event it goes full chocolate milk then takes a week to settle back to the control jar level of turbidity (12-18 inches). Anyway I pulled the water for the initial test last night, added the 1tbls, 2 tbls, ect and this morning I find the test jugs, are crystal clear but instead of sinking, the floc floated to the surface. Can say that was completely unexpected. The only thing I can figure is maybe the normal concentration of 25lb/acre foot is too high, or is this an interaction with the soilfloc and I should wait longer? Sorry about the pics, I had to crop them down to get under the size limit.

Is it just me or does the film on the surface have a greenish tint? If the floating portion contains algae, it may produce bubbles that float the floc while it decays.

My first thought was that the floaties were organic. And, yes, it does have a greenish tint. I'm not experienced, at all, with flocculants, but I would think that they would not be visible once dissolved and that only what dropped out of the water would be visible at the bottom. Is it possible that the cloudiness of the water was more organic rather than soil based?

Its possible it could be organic, last summer when it was still sans fish it would get dark green again blooms in the water column, I haven't seen one yet this year though.

Its gotten algae booms last summer before the addition of fish so its possible.

I bet if you shake the jar up it will settle and go to the bottom.

If you have algal growth present, Alum is not going to take that away. It's tied-up nutrients. Suspended sediment is one thing, algae is another. If you want to lock the algae up you have to kill it so nutrients can be released back into water so you can lock it up with Alum. Flock on the surface is normal in a pond situation that blows to one shore and slowly disappears. The test in a jar is not going to be the same thing you see in the pond.

Doesnt seem to be algae now just in the past i had blooms, interesting development though, this morning the floc in the test jars has started to sink to the bottom on its own. so maybe this will work after all.

I tried that before and it returned to the surface, but I walk out to the jars this morning and its started sinking on its own. So i shook them and set them back down to see if it changes this time.

Algae definitely will pick up the floc and float it about when exposed to sun and creates bubbles. There are likely other micro organisms that have ballast bubbles that get caught up in the floc as well and can lift it. Then there is always the possibility of adding salts that causes gasses to come out of solution, or even react with things in the water column creating gasses that would get trapped in the floc and lift it. In any case, it should settle once it is dark or the gasses dissolve back into solution.