Thanks Ari & Flashout for your replies. They are much appreciated.

Ari, thanks for the info about the lighting. You suggested 4X20W=80W. What about the watts per gallon rule? 80W give me slighty less than 2wpg. Is this ok?

Also I was looking through the DIY section and I noticed they were using Phillips PL-L tubes. Is this an option and what's the difference between these and the specialist tubes?

Lastly, I just fixed my 2 DIY fans and as of 12.30am (with one running) the temp of my tank is 27deg. I'm sure this is an achievable temp at night but on a hot day, I doubt even with both fans running, it can be achieved. Will this have any effect on my plants?