From my experience dealing with heat issues like failing equipment or insanely hot weather, I always buy my tanks an old school mercury thermometers, tried & true, never have failed me. I have owned an array of thermometer & the mercury kind are always on point. Also, I would recommend pumping the temps 1/2 a degree every other day. A 7 degree bump in less than a week sounds a bit to rapid for the coral to handle & might cause ill effect, my 2 cents. Good luck.