It doesn't look that bad in the picture. Also, its in the sand bed, so its foot may be attached to the glass bottom of the tank.
Anemones like some Nitrates and you have more than enough. I've also had experiences where Anemones that looked like yours were telling me that my Alkalinity was low.
You have a small tank, so FAITHFUL, WEEKLY 20% water changes should be enough to replenish elements consumed by your tank.
And with a Nitrate of 25 in a 12 gallon tank, it seems that you may not be doing enough water changes.
I wouldn't mind seeing a picture of this little guy under white light for a better look at its condition and all it is spewing.
I'm unfamiliar with the light, but reading the included link, it only offers a total of 36 watts of power, which may not be enough.