what does anemone crap look like ?
 

i ask because either my anemone has given birth to a white slug or it's the remnants of the half a prawn I fed it last night.

If the nem can not digest the food or the items are too large, it will spit the rest out. Nem poop is brown and looks like almost every other coral poop, just in a larger scale depending on size.

Ok thanks I cut the prawn in half I guess it was too big, I will chop them up smaller next time, I guess that the white coat is mucus, I assume I should pull it out.

You dont have to pull it out, it will spit it out and the coating will have it float and the flow should take care of the rest.