ADVICE NEEDED - Heate failure!

[GoFish]

Tanks is 46 gallon with 20 gallon sump.
Total water volume is 48 gallons

Fish: 2 clowns, 3 cardinals, 1 blenny, 1 damsel, and a rabbitfish

Corals: All types, sps, lps, shroom polyps zoa gorgonian acan

Inverts: Cleaner shrimp, RBTA

CUC: Snails, hermits

Everything looks alive and normal for the most part except for the RBTA which is doing its shriveled thing (which happens all the time anyway) and the toadstool leathers have their polyps retracted (which is also not out of the ordinary)

I don't want to cook them, but i don't want anything to freeze to death

Help much appreciated... I'll start searching at he same time
Cheers