I am going to keep this brief with the Crucial information. In short, I have a custom loop with EK Quantum Torque Fittings, EK Magnitude CPU block, EK VTX 120 pump/res, and XSPC EX280 radiator, all connected with EK ZMT soft tubing. The system seems to be running fine with no issues. The system has been running with only pure distilled water for now. I recently opened up the loop to add another fill port at the top of the loop. However, I noticed this black oil like stuff in the system. The water has also darkened. Is this algae growth or corrosion? Is this normal? Should I be concerned? I am going to be draining the system in about a week since I am taking it on a trip and am taking it drained. Should I use something like Primochill's Reboot cleaner to be safe? My best guess is it is due to the ZMT tubing. Many thanks for any help!