Jellyfish-like creature on the glass

[neuf]

I've looked at a bunch of the ID sites, and can't seem to figure out what this thing is. I've seen it on the glass on two occasions for a few moments, and then it seems to disappear into the sand. The first picture is a little out of focus, but I wanted to include a couple of pictures so show how it moves.

 

 

[awpong]

Harmless acoel flatworm

http://www.chucksaddiction.com/hitchworms.htmlflatworm

 

I remove the ones I find though.

[Trick]

kill it. you could get many more of them. I've had a whole bunch in my tank and they live on the coral. i think their a nuisance.

[neuf]

Cool, thanks.

[lakshwadeep]

I've had such clear ones before, but only one or two that never reproduced, apparently. I think mine ate pods. Not all flatworms are dangerous.