I have a 55-gallon tank and purchased ViaAqua Polar Bear chiller, model cc
-25. Easy to hook up and it brought the temp down from 85 to 78 in just a few days. I set it to cool by two degrees each day to avoid sudden temp drop, but it's been maintaining a temp of 78 for some time now and my house is hot! ViaAqua has a cc
-50 unit that is made for larger tanks (up to 120 I think). Info at www.commodityaxis.com
I paid $320 with shipping on ebay, but it's listed at $450 elsewhere plus shipping. This is an in-line chiller, not in-tank or sump. Good luck.