If you want to bring down the temperature you can do it manually with Ice nutrients.

You make up your nutrient for you tank like normal but you mix a few extra gallons and use the food storage things. They are about 4"x4"x3" thick you fill them with nutrients you just mixed. Place the lid on tight and freeze it. Make several of them and use one or too a day it will keep your water cool and replace used up water and nutrients as well at the same time. It's not as good as a chiller but it does work just more work for you.