Hi, I've fermented a Wit in primary for a week (with excellent activity) and then transferred to secondary. It's been in secondary for 10 days now. I expected that all activity would have stopped by now but I'm seeing a small ring of extremely small bubbles at the top. A closer look reveals an almost constant flow of micro bubbles coming to the top. I'm wondering what this indicates as I've never seen this before after so long in secondary. How long should this last? Must I wait longer, meaning until absolutely no activity is evident? Is this indicating a problem?