heater problem

I have a 210 gal reef tank. I previously had a 120 gal tank until a couple weeks ago. I've used a 500W titanium heater in my old tank and it would read somewhere between 78 - 80 degrees. I had the temperature probe in the sump which might have been the wrong place to put it given there are 3 pumps in the sump. Duh... Anyway I put the probe in the refugium when I moved over and it reads between 74 - 76 degrees plus it never shuts off since I set it at 78 degrees. Should I buy another heater? Do I need two heaters? Anyone know what I should do? What is the ideal Temperature for a reef tank? What should I set the temperature at?

 

78 is the standard. I run my at 75 though. What ever you pick is ok if you mantain it at that temp. Tank need 3 watts a gal. for a heater so they don't work to hard.

 

Thanks for the info. I forgot the particulars. I know I also read that you should have 2 heaters in case one breaks. I just don't want to kill any corals or fish because of the temperature.

 

alot of people do run a backup heater it's not a bad idea just keep their temp probes near each other