Flatworms in Refugium, HOW??

So I went to kick on my RO last night in my basement where my sump resides and noticed little brown FLATWORMS!!! AHHHHH!!!



I'm not even really sure what species of flatworms they are. They don't seem to have the red, or red dot, they are just kinda brownish. I'm still googling to find a positive ID.



I can't for the life of me figure out where they could have come from! I haven't added ANY new corals or fish in over 6 months! And I've NEVER seen any flatworms in the system before.



So, HOW THE HELL did I get them? And HOW THE HELL do I get rid of them??



I run my entire return through a 57W Aqua UV Sterilizer and have a 6 line wrasse in the 125G DT so that may be why I don't see any in the main DT.



To treat I'm thinking do a HOT does of flatworm exit in the sump tank then completely drain the sump and refill. After the flatworm exit I can dip/rinse/shake the Chaeto in fresh RO to help rid it of FW corpses and kill any stragglers.



The ONLY thing I can think of for a possible cause is frozen food? I have a zebra moray and usually feed him silversides, it's one of the 2 things he will eat, the other being krill, but feeding enough krill with tongs to satisfy a 2.5' eel is a PITA so mainly he gets silvers. Last week I ran out of silversides and had to pop open a flat of frozen krill for a few feedings, could they have been in the krill?



I'm really confused and concerned, please let me know if you've ever heard of this happening before and how to best deal with it...