Delestage

So to homebrewers this probably looks like racking. Which it is. But
with fermenting musts, it's called Delestage. It's the slow process of
draining the juice and then returning it so as to oxygenate the must.

2 of our 5 bins are producing a lot of H2S which smells like eggs.
Yum. No big. But time to address the prob.