Is the point of the LED to warm up the water?
No Point is if you add EPS roof u cant shine lights threw an EPS Sheet and it can cause a fire, A LED strip is safe to be in water or right on top, slim line and wont product much heat compared to other lights.
It really is the best way to go about it, I dont see the point in building a room around the tank when u can insulate right onto the tank and get better results for a cheaper price. If you build a room and you leave a gap cold air can get it and hot air can exit, Placing foam over 5 sheets of glass is pretty simple + you get a free background of your color choice. Your only down side is if you ever want to move or sell the tank you have to spare 20-30 minutes to remove the EPS.