Evening all! The light on my Elite 35 tank has just failed. Hopefully it is just the tube (although I suspect the ballast which is in a sealed unit), but OH has suggested that I take the opportunity and upgrade to an overhead luminaire - I'm doing a little dance as I type this The tank is 50cm long and the 18" Arcadia luminaire is 45cm in new money so will it extend to 50cm? We've been looking at the arcadia site but it doesn't say if the dimensions they are sold under are the maximum distance it will spread over or whether that's the minimum spread. Additionally, the one I'm looking at includes 2x14W T8's so I'd have just over 3WPG. I know that's over the 2WPG "rule" but we're talking a very small tank, so will I still need CO2 since it's so small? I really don't want to do CO2 on this tank so if I must have CO2 would I get away with dosing Excel?