water temp for coral

Many people in Florida and throughout the southern US keep reef tanks without chillers. I've been to both places and Malaysia isn't much hotter than Florida.

The key to keeping temperature down without a chiller (or constant air conditioning) is to constantly blow air over the surface of the tank and sump with a small fan. Both the sump and tank should be open-topped and you should have excellent flow within the tank. This will increase your rate of evaporation dramatically, but you should be able to keep the tank temperature in the high 20s celsius (low 80s F). Still a bit warmer than most would like for a reef, but at those temperatures, you should be able to keep most of the hardier coral species like softies and LPS.

Other tips include staying away from MH lighting and keeping fewer and more energy efficient and cooler running pumps in your tank (i.e. no Magdrives).