I'm using a biotherm 1000W right now on an old Jalli controller I had lying around.
I need to get something bigger because I have so much water and my basement gets so cold in the winter.
As for heating, it has been on for about two weeks straight right now and hasn't shut off for more than a couple minutes here and there.
I'd say it's a pretty tough heater from what I can see right now.
I had an old VIA aqua that I put through some stuff, and it's still kicking too. I think it is a 300 or 500, can't remember.
I had a 800W Jalli on another tank and that thing didn't last a year.
I either need to cap some of my tubs in the basement, or put more lights on them, or find a way to heat my water more economically. This heater is gonna bite me good at the end of this month.
My basement is low 50's at nite time.