1. will a 10" housing work? or should I go for the 20" for more dwell time. 20" feels just do big for my tank tho..
10" is enough
2. will 3/4 inlet out let work?
I used 3/4" elbow barbs
3. I will be running a inline heater should Co2 reactor be before or after the heater?
return pipe - heater - reactor
4. do I need bioballs or other media in the bottom of the reactor?
you can if you want but that's more things to clean
5. are ball values needed? what would be the benefit be ad back pressure? other the ability to service the reactor but would have to turn off the canister anyway??
I dont use ball valves
6. where should the co2 be injected? inline via a brass nipple?
7. if yes for 6 do we need co2 pvc fitting or something?
I use brass
8. the center piece of pvc down the middle is 1" from the bottom enough space?
I only leave 1/2" or less the more space you leave the more likely bubbles will make it back to your display tank, this only applies if you run high bps like I do 6-8bps
9. any updated part list or tutorials on this? seams pretty easy but I want to do it right the 1st time.
it's easy just go to the hardware store and put fittings together
If you are too lazy to build one you can try to find a prebuild one. I made this video in 2012 I'm not sure if they still sell this product, I think I got it from fleabay.