that I bought my rock at didn't even use a heater in their curing tank... I would think that there would be some die off, but it wouldn't hurt to put another heater in there. Don't worry about speed, it's not like you are microwaving the water. Those heaters take a while to heat up the water anyway. Your rock should be fine...
32 gallon hex, 34 lbs lr
, Prizm protein skimmer, fluval 104, 1 maxi jet 750, 1 maxi jet 1200 ph
, current 40w 50/50 pc
, 1 NO
powerglo 19watt, 1 daylight NO
65w (equiv), two damsels, 1 green brittlestar, 1 peppermint shrimp, turbo snails, red legged hermit crabs, kenyan tree coral, leather coral, pumping xenia, mushroom coral, green star polyps, orange button polyps