After you chill the wort, but before pitching the yeast, you need to aerate. Otherwise the yeast won't be able to do its business. For years, I tried things like shaking the fermenter or stirring like a madman. Then I read an article saying that one of the biggest things you can do to make better beer is to pump in oxygen. Here is the device I made to to it.
Step 1: Cut Pex & Instert Stone
The stone barb is 1/4" and so is the pex.. I couldn't force the barb into the tubing at room temperature, so I stuck that end in some boiling water for 5 minutes . When the tubing was hot, I was able to get the barbs all into it (see pic). Don't burn your hands; use a towel or oven mitt to hold the hot tubing.
Step 2: Connect Tubes
Set up the sleeve & compression fitting as shown...
I used 5/8" and 9/16" wrenches to tighten up the fitting. Now that I'm done, I wonder if I should have used one of the plastic sleeves that came with the insert. When I turn it on, I hear no leaks, and the stone bubbles in water, so I'm not going to worry about it.