Heizung wohin?

If this was my grow. I'd place the heating mat under the black tray that's under the white reflective liner. White liner - top = Black tray - middle = Heating mat - bottom The black tray will act as a even surface between the heating tubes or ridges within the mat and the white surface. Ideally I would use smaller saucers for the individual plants vs a big one. The big black one prevents the light from reflecting back up from the bottom of the tent vs using the white liner. I also don't use heating mats I find they heat the medium up to much and cause problems. But if all you have I would set it on low to low medium if it has any settings. Best Of Luck!