Good Afternoon, my wife and I purchased the AQUARIUS LOUNGER 4 years ago. We have been quite religious about keeping it clean and changing our the water and balancing the chemicals. Since the beginning there have been small black pieces floating about. Not mold or debris but malleable and can smear between two fingers and smells like oil, or tar. Whatever the water level is in the tub a line of this stuff that sticks to the walls and needs to be scrubbed extremely hard to get it off, even after a full filter and water change. We thought it was pieces of tar shingles on our roof at one point. The hot tub is located under the deck and when it would rain sometimes we found tar from the shingles on our deck, we assumed when cleaning the upper deck they may have been falling downwards. But the tub is covered at all times so we ruled this out. We are just wondering if this is something that was left in the pipes during the manufacturing of the unit and is breaking down maybe? We just want to know if this is common and if anyone has any experience with this at all. We have called techs out and they have not been able to diagnose completely. One saying its a bad balance of chemicals which is not true because we keep on it. The other saying it needs a flush which we are going to do, and hoping is the solution, any help is appreciated. Thanks very much.