Please rehome that paradise fish. I have a trio myself and they are very active fast swimming little things that really deserve an absolute minimum of 2ft of swimming space. They have an intelligence and insatiable curiosity similar to the larger preds (and a ferocity to match) so he is likely bored out of his mind too. To those saying get a heater, its probably not worth it unless the tank is close to freezing. These fish are very hardy and do very well at room temp or even in ponds if you live somewhere it wont freeze over. I know how easy it is to make these sort of mistakes but a little research would show you how colourful a healthy paradise fish is. Here are my ladies and they are no where near as colourful or as large as a male:
I started out with them in a 29g but they needed more space and are now happily enjoying a 75g with the male and some fast swimming shoalers but as you can see they still spar over territory.
My fish is quite happy in his environment. I don't know where you get 2ft of swimming space as their natural habits don't typical support that. As far as being bored I guarantee my fish gets more attention then yours do. I sit a play with him throughout the day, 8 hours a day 5 days a week. When I'm not around for those 2 days my cube mates often come over to say Hi.
He gets fed live food weekly and I stock the tank with small pond snails that he spends much of the day hunting for and eating. He is constantly active and entertained.