HI I'm Tila and I'm new here and a beginner in keeping fish so I don't really know much about them first hand. I got 2 moor fish a little bit more than a week ago and they were looking fine till yesterday. Today I noticed that their poop (tmI I know) is changed colour like off white and it can get quite long. The only thing that I did different I got a new big filter which is probably to big for my 18 l tank ( eheim 160. After reading a bit it looks like parasites but I'm not sure. Help me please as I already love them and don't want them to die.