I ran both hoses and only one had black stuff coming out.
I then removed both hoses and ran the water, collecting right away and a few minutes later. The front had normal water. The back (with the black and foamy water) had nothing in it once the hose was removed.
However, I've had no foam in winter, last I saw it was summer, so I can't explain that. But the black stuff apparently is from the old, black rubber hose which im going to need to replace with a new hose.
