Well lately these brown things have been popping up and I just thought they were diatom algae so i siphon them out every water change, but they just keep coming back. I thought it might be because i might be over feeding so i reduced my feeding. However, today I did a water change and siphon out the brown stuff and I was curious this time so I just studied the brown things. Turned out they started to move around!! I knew then that it was flatworms. What should I do?? Are they a problem? Will a mandarin eat them??