Originally Posted by Gunderman456
No danger, mine is at that level right now. There is no way air will get to circulate if you have your hose attached to bottom of the reservoir.
The gunk and its origins is another story. It might be something already inside your loop, or the top of the reservoir is exposed directly to air when it should be caped.
Of course it's capped and air does not circulate. I'll monitor it now. I was wondering how much of an effect does that trapped air (which is fairly impure) has on the loop's evolution as in the past I noticed the walls getting green deposit (was using the EK-Koolant Clear, the one that turned yellow in the bottle in the 1st post).