Greetings! I just went to empty out and clean my 2 gallon tank that I keep my developer in, the type with a spiggot for pouring. It had contained Ilford ID-11 that was mixed nearly 2 months ago. I had mixed up 2 liters of ID-11 and put the floating lid on top and put the main lid on and used up most of the developer over the past 2 months, there was about 6ounces left. Upon opening the tank I found a black liquid on top of the floating lid, and along the wall of the tank there was what looked like splashes of the same liquid. The splashed areas didnt come off with rushing hot water and only came off with a minimal amount of scrubbing. The total amount of this black liquid might have been 2ounces at most. Under the lid the small amount of ID-11 was perfectly clear and fine (well that was until I accidently spilled the black stuff into it). Something that might have some effect this situation is that I taped the main lid onto the container so it was more rigid when I moved the tank to where I store it, 2 pieces of duct tape one on each side. The lid doesnt ever sit on snugly on these containers making them seem a bit wobbly to carry around. Im guessing this was some sort of bacteria or fungus? Has anyone else experienced this? I was pretty sure that everything was dry when I sealed it up and and I am also sure that I didnt leave a bunch of water sitting on top of the floading lid. I was about to mix up a gallon of D76 but now I am thinking to wait a bit to see if this could be harmful to my developer or if it should just be ignored as a commonplace thing. Also, any tips to avoid it in the future would be nice, if it does turn out to be a problem. The tank is stored on a high shelf in a basement with a temperature thats constantly around 68F and about 40% humidity.