Can anyone help?

[kris_willard]

I found 2 of these little guys on the back glass of my nano and was wondering of ne one knew what they were. They are about 1/2" long and seem to suck the glass to move. Are they good or bad?http://www.canreef.com/photopost/showphoto.php?photo=813

[smokinreefer]

looks like flatworms.

i have never found them to be harmful in anyway, except to the aesthetics of the tank. they can quickly become an eyesore if allowed to overrun the tank.

do a search on them, you will find many many threads on the subject.