I'm kinda crazy on heaters, as others will tell you ...
Just look at my build thread
I have 3 x 200W on my RKE, and a pair of 250W on a Ranco, just in case
All in a 75g tank ( 110g total with sump )
I agree with everyone on the idea of using multiple smaller heaters, instead of one or two larger ones;
With one or two large ones, if one fails on, it may cook your tank
With one or two large ones, if you rely on them both, and they both fail, your tank is doomed
With two or three smaller ones, if one or even two fail, one will still be adequate to keep your tank going short-term
With two or three smaller ones, if one fails on, it will take longer for it to cook your tank
I set all my heaters in a bucket so they are max 81 degrees F
This way, if a controller fails, they won't cook my tank
Next, I installed 3 x 200W heaters controlled by my RKE
Next, I installed a Ranco controller, with 2 x 250W heaters set for one degree below my target temp, in case the RKE or such fails
Hope that helps
