Postby Teapot1 » Fri 02 Jun, 2023 01:25
Your water quality is so poor its hard to tell, have to take your word for brown, ok hard truths over with, it could be metal staining although that is usually more widespread. Did the stain appear after shocking? I would still try vitamin C tablets on the staining to see if it lightens/fades, just hold vitamin C tablets or powder in a suitable sock on the stain for a few minutes and come back. What type of filter do you have?
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
20230601_172736 by writermedic, on Flickr
20230601_172708 by writermedic, on Flickr