unkown

Can’t figure out what kind of fish this is. Came in on a rock as a hitch hiker and lived in a dark bucket for a period and has been in my tank for years. Here are my best pictures. What do you guys think?

I came home today and Saw that my Clownfish was not as active as normal so when I went over to double check I saw that it has a giant grey streak on its body and seems to not be well. I have had them for only about 3 months now. I have no clue what this is or how concerned I should be. Right now...