It all depends on how much you feed them, you can kind of control their growth rate..to a small degree.. the more you feed, the larger/faster they grow... or you could never feed him and just let him grow naturally fromt he light.. and that would take the longest time to get him to his max potential.. ...
And yes, given the right circumstances... proper lighting... you could get away with never feeding your anemone.. as they feed themselves from the light. as you can see he is sitting in the middle of the tank, and on this tank i got 2 - 250W MH 20k bulbs..
that other one with the pink skunk in it... is sitting to the Far Left of the tank towards the bottom of the tank... under 2 400W MH lights 20k bulbs.. thats a standard 150g Tank so the depth of the water is deeper, im honestly shocked he chose to sit so low, as for the big purple one is in a shallow tank where the depth is only 13'' apose to 24'' deep.
what i was getting at with the lights and tank depth.. is these are high light creatures, they crave light..
and before i get asked this.. the people who didnt read prvious posts.. YES they can survive under LeD's... in fact, they LOVE LeD's... if you asked me, only reason i switched to Metal Halides was to see if i got better color/growth out of my SPS..