dav4 Nice set up. I am skeptical about the mulch doing much of anything heat wise but flower pots and that (very heavy) water bowl (I have same one) are a different story there is 3-7 pounds of thermal mass there representing a fairly large amount of floor space.

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No thermal mass.

Question, I am guessing your probe is on the floor? If you are seeing that much effect to ambients are you not concerned that the snake may lay or poop on the probe causing the panel to spike up in temp and take the ambient air temp with it? The reason they are safe is they don't be inherent nature heat the air so as long as the floor doesn't get too hot (mine does however) and the snake doesn't lay against the panel there is no way to get burned. If you are seeing 10º at 90 I would extrapolate 20º at 100 and close to 30º at the max temp of the 40w panel (mine is a little over 190ºF RB says 190º). I no longer use mine it is off just UTH and lights I have no problems at all the RHP made no difference at all. I actually after my experiences and this discussion has strengthened the belief they do not belong in enclosures less than 18 inches the reasons why they are 'safe' in short enclosures get negated by the proximity to the floor. If it heats the air they probe needs to be treated like the probe for a UTH (my hottest caps at 160 and most 100º) and kept so the snake cannot be in between the heat and probe (in it is on the floor between that and RHP in the ceiling) and if it isn't heating the air then why use one at all unless you need a gradient that goes up and down not across?