Bala, where do you live? Is the temp starting to raise there now? Why don't you wait until it gets a little closer to summer and keep an eye on your tank temp thenm if you need to invest in something you can start weighing your options based on how high your temp is getting. Like previously stated, you need to move your tank from the window, that will help considerably. You say you have a 10 gallon, mine came with 2 incadescent bulbs, go to WM and get a couple of Light of America screw in compact flourescents and that will help lower your temp CONSIDERABLY! they are also more energy efficient. You could try hanging dark curtains to keep your room cooler. All of these things will help without having to spend a whole lot of, probably unnecessary, money. Again though, I would wait until the temp starts rising enough consistently before I began worrying too much about it.