It's not going to have any real noticeable long term effect. The tank volume is just too small to disipate the heat fast enough compared to the rate of input from the filter.
A fan across the top of the surface of the tank would probably help. However the best solution will be to increase tank size or go back to the sponge filter.
A fan across the top of the surface of the tank would probably help. However the best solution will be to increase tank size or go back to the sponge filter.