As the title suggests, I have a 120x40x40cm tank and I'm thinking of going down the pressurised CO2 route. However, I'm concerned about getting the distribution right on a tank this size. At the moment I'm running a Fluval 405 with 2x36w tubes. I've only used the Nutrafin system on my smaller tank so know very little about the practical side of adding CO2. I'm not going to do this for a couple of months so I want to make sure I getting all the right stuff first. Am I right in thinking that 2 diffusers are better on a tank this size? Also,would a spraybar help with distribution? Basically, any help on doing this would be great, esp the best way to set it up on a largish tank!