Before going the route of a chiller I would try a few other things (I've never run one, but from what I hear they draw lots of energy = really expensive to run).
I would address the amount of heat going into your system. The Mag Drive 18 is a 150 watt pump. According to this site (http://www.beananimal.com/articles/thermodynamics-for-the-aquarist.aspx), "almost 100% of the energy consumed by a submersible pump (mag-drive, powerhead, etc.) is converted to heat in the tank!" Assuming you have ~6' of head pressure, the Mag 18 is doing about 1,125GPH on 150 watts. It's the equivalent of having a 150 watt heater running, 24-7. You can swap that power hog out for a Laguna Max Flo 2000 (PT8244) that does 1,360GPH @ 6' head on only 80 watts (the 2011 and older models draw 100 watts, so you'd probably want to make sure you get the PT8244 which came out in 2012). Going with the Laguna would reduce heat into your tank by 70 watts which should reduce your water temp and your electric bill and give you a couple hundred extra GPH...that's a win-win-win.
You can try running a fan across the top of your tank or sump; you can control it with a Ranco ETC temp controller set to power the fan "on" anytime the tank temp exceeds 82F. Fans are going to be a whole lot cheaper to run than a chiller, so if after swapping out the pump reduces the temp by a few degrees, the fan may be enough to bring you to where you want to be.
I would also limit the amount of time your lights are on, since the heat they put out are contributing to the problem.
I would address the amount of heat going into your system. The Mag Drive 18 is a 150 watt pump. According to this site (http://www.beananimal.com/articles/thermodynamics-for-the-aquarist.aspx), "almost 100% of the energy consumed by a submersible pump (mag-drive, powerhead, etc.) is converted to heat in the tank!" Assuming you have ~6' of head pressure, the Mag 18 is doing about 1,125GPH on 150 watts. It's the equivalent of having a 150 watt heater running, 24-7. You can swap that power hog out for a Laguna Max Flo 2000 (PT8244) that does 1,360GPH @ 6' head on only 80 watts (the 2011 and older models draw 100 watts, so you'd probably want to make sure you get the PT8244 which came out in 2012). Going with the Laguna would reduce heat into your tank by 70 watts which should reduce your water temp and your electric bill and give you a couple hundred extra GPH...that's a win-win-win.
You can try running a fan across the top of your tank or sump; you can control it with a Ranco ETC temp controller set to power the fan "on" anytime the tank temp exceeds 82F. Fans are going to be a whole lot cheaper to run than a chiller, so if after swapping out the pump reduces the temp by a few degrees, the fan may be enough to bring you to where you want to be.
I would also limit the amount of time your lights are on, since the heat they put out are contributing to the problem.
