Well, not sure what size your biocube is.
I have a 14g Biocube and I will be using a Eheim Jager 50 watt. It fits just enough lol. I have Aqueon Pro heaters in my other tanks, and I DO NOT like them...the temp always fluctuates.
Don't try to fix something that isn't broke. You just might end up breaking it
30g FOWLR Tank
8g Mantis Shrimp Tank