I walked Millie around the lake at Hillfields Park the other day and was alarmed at the black sludge that appears to have come from an outlet from a commercial property on Monkspath Business Park. I took the videos shown below: There was no way Millie (my dog) was going into the water.
The views are self explanatory and I have requested an urgent inspection to identify what the black sludge is and what risks it poses to our wildlife, fauna, children and animals.
I will update you as soon as I can.
Ken Hawkins 
I’ve noticed this too for several days now during my daily walks in Hillfield Park, Ken, but today (Sunday morning) it seemed to have cleared somewhat. As you say it would be good to get to the bottom of it, so to speak.
Many thanks Rohan. I will pop down and check tomorrow morning. I have had reports of discolouring but was advised this may have been residue from silt being washed down stream after heavy rainfall. This black sludge is from another source.