Here is what I did for my 55 gallon tank:
Rapids Wholesale - Co2 kits - 5-lb new steel tank with dual gauge regulators
$99 (#BD435) http://rapidswholesale.net/Merchant2...uct_Code=BD435
Florida driftwood - needle valve used in medical gases $19.50
Appears to be Clippard MNV-4K2 (4k2 has an 1/8 hose barb included) http://www.floridadriftwood.com/product.asp?3=51
Also needs a Â¼â NPT male to 1/8â NPT female adaptor (Clippard #15006-5) to connect the valve directly to the regulator.
Can probably get where you fill co2 gas.
Plant Guild Power Reactor http://www.familychest.com/plantguil..._reactors.html
Note some online aquarium stores now carry the larger version of this, which is what I have.
CO2 Level Monitor
Dupla monitor - Dupla CO2 Dauertest http://www.dupla.com/start_e.htm
You may be able to buy the clippard needle valve - MNV-4K2 from a local Clippard distributor. Check their web site www.Clippard.com
Some people use other co2 reactors/diffusers. Lots of variety here so do some more research on the web.
My 5 lb tank lasts about 8 months.