Sacc - I don't know what a fish tail is, but I don't think my wife will let me get one! I second the welcome back to a great contributor here. Nice article reference. I will read this tonight.
You can see them on the side of the fermentation vessels in this picture:https://commons.wikimedia.org/wiki/File:Black_Sheep_Brewery_Tour.jpg
They're basically just sprayers. Fermenting wort is pumped through them and sprayed back on top of the fermentor, re-aerating everything.
IIRC, some brewers remove yeast throughout fermentation, and basically keep the yeast multiplying throughout fermentation, as opposed to just in the beginning as we fo.