Thank you all for your advice. I am going to leave the tank as it is. All the fish in there at the moment are doing great. The betta is very active and loves hidding in the plants that I have in there, then popping out now and again to say hi. He is not at all sluggish and goes up to the top now and again for air. All the other fish are doing great too, active and eating. I think I am going to leave it as it is for fear of hurting or killing any of them. I think that I may need a new heater though as I set it to 75 (the next notch on the heater) and it was up to 82 and still increasing. It's back at 72 now but maintaining the 74-78. I can safely say I wont be going back to where I bough the tank.
The tank does have a hood, I have heard that fighting fish have a habbit of jumping!