I also have used the frozen bottle trick to lower the temp in a hurry. My a/c went out last year and all my tanks shot up to almost 90!!! I just stuck in bags of ice into each tank and it lowered the temps quite a bit. Not a perfect solution but good in an emergency.
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.