Heating issue

[authentic]

I was using 2 cobalt neo heaters in my 140 and my temp was swinging between 77-81.bought a finnex 800 on black Fri and plugged it into my apex on #6.tank immediately heated to 82 when set at 78 on the controller.is this heater too poweful?is there a difference plugging it into a relay outlet? luckily my lights shut off to warn me of the temp rise

 

[120reefkeeper]

This is how I have mine set up. I have 2 heaters. 1 set as primary at 78F controlled by Apex. Comes on at 77 disables at 78. This allows me to keep a very tight temperature tolerance with pump heat and lights. Fans also controlled by Apex turn on at 78.5 off at 78.3

#2 heater is a cobalt controlled by Apex. Set at 76F off at 78 this is set for a primary failure. If it cycles I know primarily has failed.

Also cycle out primary heater once a year and use backup as primary and buy a new backup

 

[saltyphish]

what size heaters?

 

[mmw64]

interested in what size heaters also.