Hey i believe that this question has been ask many time.......... A chiller is not a must in a reef tank unless you using very strong lighting that give out lots of heat such as metal halide....... But even then if your temperature remain at ard 28- 29, you still need no need to use a chiller, btw if you find chiller expensie you can go for cheap AC/DC fan, they are able to reduce a tank by 1-2degree....... But you must bear in mind once you use the fan, water top up will be very regular and quick.................