Well, that wasn't what I wanted to hear, but at least I know what make of heater to buy. 
Ive been thinking about the tank and read in the articals section that you can recreate the original environment of the fish? ( Ive forgotten what its called.> Biosphere<?) 
I have been given quite a list of fish which will go well together eg. 
 
Tiger Barbs, Rams ,Kribensis, Bristlenose, Bala Shark,Rummnose Tetras,Harlequins Rasboras, Plus 
 
Plants .Aubias,Crypts, Java Fern and Swords. 
 
Do these lend themselves into a  theme of some sort? does it have a name? Cheers Bill.