I have not read the entire thread but from the first post I can confirm that I get a brown scum growing on the sides my saltwater mix up can when using Oceanic. I do not get the things like you have in your can but have seen an odd white substance that will not disolve in some of the batches I have mixed up. Mine does not get any direct light at all. Just a little bit of light from the room. I too am almost positive that Oceanic is what caused my algae to return. I poured about half of a 90 gallon jug in the trash over the weekend. It may just have been that jug. Using the same 90 gallon jug I did a 60 gallon change on 250 total system gallons (when I removed my DSB from my refugium)and my half of my hammer coral that I have had for 4 years bleached out. I was removing the DSB to try and trouble shoot the return of my algae even though all parameters are in check. The hammer coral has since recovered and I will not do any more changes with Oceanic salt. In the past people have criticized some brands and products and those makers have come here and defended themselves. I would like to see oceanics response to all of this.
About the "just hanging a halide over any saltwater would grow the brown slime". Although this might be true if you used a light, I have no light and with Oceanic I get the brown slime and also some sort of slick coating that forms over the clear tube that I have hooked to a pump that sits in the trashcan. I also have an airstone in the bucket constantly. I never had any of this with IO.
I loved Oceanic to begin with, mixed well, corals seemed to like it, but as I used more and more of it I have the worst hair algae outbreak I have ever had and my hammer coral now bleaches a little bit with each water change. Back to IO or something else for me.
Ebacon, the pump never contaminated the IO salt in mix up and evey time I did a water change I have been wiping the brown stuff down and sterilizing the can with white vinegar. The pump has also been soaked in vinegar as part of my regular maintanence to get rid of calcium build up. I put that pump in with the rest when cleaning. I will doing a water change this weekend with something other than Oceanic and I will let it sit for a day and see if I get any brown stuff.