...update
Got the diffusers but the pump won't be here this weekend, bummer.
Since I already have a shop compressor, I've decided to procede with 15 minute thing so it'll be ready for full duty next week.
Here are the deffusers...
1mm slits, I think.

Installing the PVC...

Decided on a temporary setup using a reducer
to use a temporary 3/8", $21 air hose till I get the 1" permanent setup. I need an extention air
hose anyway...

Had to convert my tyre inflator to keep
the pressure at 5 psi. Pressure regulator on
the compressor only goes down to 60 psi...

Finally the results - a nice, stinky boil.

I'm glad I got this show on the road, coz my cat fish has been gasping for air. That's not a good sign for a bottom fish.
Will keep in touch.