for any corals to thrive..
you need to have temperature ranging 26-27 degrees
once your temperature reaches 30deg, it will release zooxanthellae which will make your corals lose its colour..
if you find that u can keep your tank temperature constant with the fan between the temperature region..then i guess u wouldnt need a chiller..
but a top up of fresh distilled water is necessary as the fan would increase the rate of evaporation