Yeap like Bro Alfa said.
MH, return pump (assuming chiller return back to main tank), skimmer, CR all can fail but not the chiller or chiller pump
Best is to get a backup (I want but pocket won't allow)
I know the importance and I almost kanna because my resun MD40 running my chiller up lorry on one monday but the lucky thing is I am still asleep and the damn thing got burned and tripped my house ELCB so I had time to make corrective action.
If that happens 2 hrs later when I am way to work, then still okie because my UPS would have kicked in and my tunze will still be running but sooner or later the temp will raise and all my SPS will up lorry