I'm using this on my WC loop. It's been working fine for about 6 months now, until I inspected the loop a few days ago. Some green "stuff" is starting to form around the outlet for the GPU block; this "stuff" has the consistency of ear wax so I guess is fungi or something. Weird thing is that that's the only place it forms. I already cleaned it several times but the thing grows back on. Overall cooling quality hasn't changed much and I plan to flush the system soon anyways, but I would just want to know what the "stuff" is.