Thank you for your replies. I had read somewhere that Ancistrus tamboensis was somewhat flexible regarding water chemistry, and I was looking for verification. I'll keep searching for a way to rid myself of this brown sludge on the glass and rocks.

I was wondering if anyone had had any success with keeping a suckermouth catfish with Lake Malawi cichlids. My pH is 8.0, and the GH is about 15º.