1. The brown water at the bottom of the tray is certainly not slime or
sludge, as it developed in 8 hours. It was pretty obvious looking at
the metalic heating element that there were rust spots. Depending on
where it was made, the metal material/alloy may have had some corners
cut in the mixing of materials.
2. The unit might be merrily steaming away, but it has turned off
inexplicably. The humidity setting was high, and the relative
humidity was only 30% (30-50 is good for humans). I have to press the
Start button to get it started, but this leaves open the possibility
of waking up to dry lungs and realizing that the unit turned off early
in the night.
Still trialing this unit, will post back.
Your machine may require frequent cleanings, depending on the quality of
the water you use, among other things. If you can afford distilled
water, try that, or a Brita or similar filter if you aren't already.
Spring or other bottled water obviously won't solve this problem - you
want water as pure as possible, not with a lot of "good for you"
minerals in it since they're bad for the humidifier.
-S-