If anyone could source me some cheap CO2 (non fire extinguisher) then I'd be grateful. 600g welding bottles is the cheapest non FE isn't it? Also how long would one of these run on my 120l? By the way solenoid is preferred since it will pay itself off. http://www.aquaessentials.co.uk/index.p ... th=194_247 Can this be used with welding? And is it good (cheap and good wise). Any good ones on ebay?