Fat Sack Storage

A site visitor asks, "We bought a fat sack this summer and have been enjoying it. But I'm wondering what we need to do to store it for winter. Using it in the river it no doubt has some algae and bacteria inside and I don't want that to grow inside. Obviously I can rinse it out - but should I use some Clorox or other cleanser to sanitize it? If so - how much?" - JSTMK Does anyone have suggestions for JSTMK? Please post them to the forum.