I use a super hot water solution of one quart bleach to 5 gallons water. Let it set, slosh it around, dump and rinse. This not only keeps my live & baitwells fresh, but it kills the freeloaders (zebra mussles, etc.) that I might have picked up in my travels. jerr- – – forgot to add- – run it thru the recirc pumps, too.
I field tested a product called Bio-Safe Live Well Prep, made by a company called Renew Allure. I’ve only seen this product at a few marine dealers, but if you can find it, it does get rid of the slime, smell or any other odor in your livewell.