ADVICE NEEDED - Heate failure!

[GoFish]

Actually user failure.... i accidentlay unplugged my heater last night.
Theres only one and its in the display tank.
For some reason i just looked at my floating glass thermometer for the first time in a month or 2 and it says 70!!
I looked at my reefkeeper and it said 69.6!!!

I just plugged my heater back in including a 2nd heater (also in the display). How many heaters should i use? i have 2 more if need be, I'm thinking of throwing a 3rd one in the sump, or take the second out of the display and put it in the sump instead.

How slow or fast should i go? The tank normally runs at 78.5 and has been unplugged for 22 hours.

Livestock info coming next...