Join Date: Apr 2007
Location: HI, but Pueblo, CO for now
I would watch your pump carefully. Being on the input side, you do run a risk or losing your siphon. With diy co2, it shouldn't be a huge issue but it still might happen. I would put the reactor how you had it, on the output side. Don't worry about the pressure. When you turn your filter on, then there should be little to no pressure to cause any blockages.
Since you are in no rush, piecing together a pressurozed system might be cheaper than a prebuilt one. Constantly check ebay. There's a bunch of surplus dual stage regulators and needle valves that will work for our application. Shipping might kill you if you can't find things from your part of the world.
You could save yourself some trouble and get a prebuilt system. I prefer the guys at sumoregulator but there are others like gla and rex. You can get a really good regulator for around $200. Then all you need is a co2 tank and diffuser/reactor and you are good to go.