its not enough. for a 12gal u need a minimum of 50 watts of T5's or Metal Halides. ive tried an anemone in my 12gal JBJ it did ok for about 2 months then i gave it up cause it was getting unhealthy. but if u do decide to go with an anemone u need to feed it once a day or every other day to keep it healthy.
I have a Green BTA in my 12 gallon deluxe with the factory lighting 2- 24Watt 50/50 pc's...
He loves life...my 2 clowns are always in him and his tips actually are extremely bubbled and his coloration is awesome!...I do feed him a little silverside piece every 2 days though...
when i first got him he roamed the tank for a week straight and even almost died cause he was stuck in the overflow inlet...
he learned his lesson and now is stationary front and center...
Good luck!