For all you dedicated dry fly fishers I came across this on another site so thought I'd pass it on. The fumed silica many of us buy in bulk and use is about the same as Frog's Fanny for what it's worth. I've used Aquel for years and it is great for keeping yarn indicators floating--not good for CDC winged flies. The Frog's Fanny/FS works great for the cdc though.
http://troutster.com/fly-floatant-test/