Thanks again everyone. I'm looking fwd to seeing its final form as well.
That was my first thought. JB Weld itself is rated to constant 500 degrees F, and there's no way your lights are gonna get that hot!
Yeah, I'm not worried about JB Weld withstanding the heat alone. I've used it on a few automotive projects where plugging a hole was in order and it definitely stays put. But I'm uninformed and thus concerned about its bonding properties, even w/ just a little heat, when used between 2 flat surfaces instead. Next on the to-do-list is bonding a sheet of metal to the base, that goes under and thus is weighed down by the aquarium. The weight of the top part of the light will require a good bond between the base and this undersheet. Anyone have opinions on whether the JB Weld will hold? Sure, roughing the two surfaces up beforehand should help but will it be enough? Or should I stick w/ the tube of metal epoxy I also have on hand?