Flakes like that are most commonly calcium flakes that come off of SWG cell plates. The cell if full of tiny bubbles. They might well float for a time.
Calcium hypochlorite in granular form is not crystalline calcium hypochlorite. As described in this link the bulk density is 64 pounds per cubic foot which is equivalent to 1.025 g/ml so roughly the same as water, but of course that includes the air gaps in between granules. Nevertheless, the granules are not crystalline calcium hypochlorite but are rather compressed from fine powder so that they dissolve more readily. Such compression traps air inside the flakes so that they are only somewhat denser than water and some might be less dense and float to the surface until they dissolve. Of course, any granules on the surface can remain there from surface tension of the water even if they are denser than water, but the ones that float back up most likely have enough air in the granules and possibly on their surface to be able to float back to the water's surface.
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Welcome to TFP! For a wealth of pool care information please check out our free Pool School. If you are in need of specific help then we encourage you to Register and ask us here in the forum!