Anemone will do fine with no feeding or minimal feeding. If you can control yourself, stick to not feeding him, and start out with a small anemone, you can keep him in a 40 g tank.
I keep my Magnifica in a 20X18X20 inch cube for several years, no problem.
I had my Blue Haddoni in my 24 g Aquapod for 3 years with no problem. I just recently move that Blue Haddoni to my 360 tank, and sold the 24 g cube.
The key here is feed sparingly to keep them from growing. Given good light and water condition, they will do fine. If you don't give them the raw material and the energy, they will do minimal growing if any. Plenty of us have anemone shrinking from not feeding, but they are fine and have no problem.