Keeping your nano reef's tempterature under control can be challenging in warm climates. The most common reasons for needing to cool a nano are to offset heat from intense lighting or offset heat from the room itself. There are two methods used to chill a nano reef that are reliable. The best method is to use a micro chiller. This is a new product that uses heat exchange to cool the water, and can cool the water 5-10 degrees. It is mounted somewhere on your aquarium, either in a hang-on-back filter or directly mounted to a bulkhead in your tank or sump. They are a bit expensive, usually around $120, but much less expensive than a regular aquarium chiller. More information on these can be found at Marine Depot.
The other option is to use a small fan. A fan provides a cheap way, usually $15, to cool a nano reef. To do so, position it so cool air is blown across the surface of the tank. You will notice a temperature change of about 3-5 degrees. Remember that this method will cause a lot of evaporation, so you will need to be sure to compensate with top off water.
If the heat is coming from your lights, and you don't already have one, install a fan to blow air into to canopy, or reverse so it pulls the hot air out. Be sure to leave another hole opposite the fan for air to leave/enter. If you have a large enough fan, this may stop heat transfer to your nano altogether.