1 1/2 inch brown flat worm in my filter sock?

[thefullgonzo]

Well my 9 year old daughter swapped out my felt filter sock in my reefer 170 tonight (she really is involved with my tank and loves to watch it and do the testing). I was flipping the sock inside out to clean it and noticed a 1 1/2 inch brown flat worm crawling around on the inside of the filter. It resembled a leach to me. It it something I need to be concerned with?

 

[Hotelbravo]

pictures would really help to figure out what it is.

 

[thefullgonzo]

Thought of that after I flushed it