Hi all, Got a question regarding heating. I'm starting my first custom build and I'm in the planning stages. I know what I'm going to do (silicon in, expanding foam above, grout, then paint, then varnish) but I have a placement question. I'm wanting to keep the rest artificial for now, so I can then plan an update to full naturalistic once I see how this goes. Can I place a heatmat under the expanding foam / silicon (as in outside the tank below it), or must it directly heat the substrate? The physicist in me says it's a good idea, as the expanding foam's air pockets will aid heat retention, but I wanted a bit of guidance and advice before I go ahead. There will be floor space for the heat mat to heat substrate directly if that is preferable. Any and all advice welcomed and appreciated. If you have bonus tips about other build points, much appreciated too! Geordie.