Have you thought about placing the heater horizontal with suction cups about an inch above the gravel behind some of your ornaments? I just have mine in the corner, but when I set up my 55G with 2 heaters, they will be horizontal along the bottom, about an inch above the gravel, behind my shipwreck and driftwood. And I'll use a small amound of aquarium-safe sealant to hold my power cord in the corner of the tank from top to bottom. That way if I need to replace the heater, just have to peel the cord away easily.