The snot from the anemone could be what ever it ate ,
It's mouth is also where it expels waste from .
Stress is another reason for it to expel waste .
Colour and appearance is a sure sign of a anemones health .
If you are having diatoms , it would be a new tank.
Housing a anemone in a new tank is only asking for trouble .
bacteria is a indication of high nutrients . Either nitrates , phosphates .
Anemones require good water quality with low nutrients this could be the reason for the slime, snot being expelled .
Have you tested ?
Some test might be 0 or low but seeing algae you will not be able to test the levels cause the nitrates , phos is being used by the algae .