Two low cost alternatives to a chiller:
1. There is a good DIY project using a small dorm fridge that works good.
2. A room A/C unit near the tank blowing set at about 74 would work too, plus help cool down the room it's in just a touch. Just don't blow the air directly on the tank, as it comes out at 55 degrees.
The DIY project would probably cost about $150 - $200 and the room A/C unit $200 - $300 new, but you can often find them used for a lot less. HTH