I have a BioGuard Mineral Springs MS-10 SWG. Yesterday I went over to the filter area to just take a look at everything and noticed a couple of black drops on the slab below my SWG cell. After further inspection, I see that it is coming from the SWG cell itself. It almost looks and feels like dirty black motor oil.
To add a little extra to this... I recently had an algae outbreak and added chlorine to boost my FC up to shock it. I then set my SWG to 100% and switched the boost on. I did this for a few days. After testing, I notice the FC has climbed to 40ppm so I then decided to shut off the SWG all together until it comes down to around 10ppm then turn it back on setting the output to about 75% to gauge it, especially since the water is clear now.
Not sure if that has anything to do with the black stuff but thought I would add it just as extra insight.
Does anyone have any ideas what this is and what may be causing it?