You can build your own chiller more MUCH less than a commercial one. I posted a DIY chiller link previously. All you need is a dehumidifier. I just bought a 30 pint unit for $30. It will easily cool up to 60 gallons of water! You'd likely need to have a much bigger res though. I'm using a 24 gallon tote that will feed up to 4 buckets. 10 minutes every 4 -6 hours will keep res temps in the 64-70F ( 17.7 to 21 C ) range. I'd use the largest res you can fit in your tent, and insulated it well. As an experiment, I put a 2.5 gallon bucket in a box filled with packing peanuts for insulation. The temps slowly climbed from 60 to 70F over a more than 24 hour period.