I've kept anemones in all my tanks, 14G to 155G and under all types of lighting, LED, PC, T5HO, MH.
Here's the issues:
Nems need PERFECT water parameters. An anemone should not go in the tank of a new hobbyist. A new hobbyist or even a seasoned one should not purchase an anemone unless they really know what they're looking at, because there are a lot of unhealthy, yet still colorful anemones out there. Someone who doesn't know what they're looking at goes, "That's so pretty, I want that." They bring it home, it dies in less than 6 months and they wonder what happened.
Anemones will usually move around when first introduced to a tank, but usually will eventually find a place to call home that makes them happy. If your anemone never settles into one spot, it's not happy. Changing the flow every other day to try to make the anemone happy will only aggravate it more, a lot of people do this and in turn, the nem suffers and dies.
Feeding:
You can't just place food on the anemone and expect it to eat. A) It needs to be hungry and B) The pieces need to be small enough for it to digest. I NEVER feed anything other than the food I feed my fish, regardless of the size of the anemone. I've noticed that with large anemones, if they get accustomed to eating larger chunks of food, they are more likely to grab a fish. Keep the pieces small. I just shoot a little fish food in their direction during feedings once or twice a week. Let the food flow through the tentacles rather than just plopping the food on the mouth.
They can survive in smaller thanks, for your tank, you'd be far better off with a small BTA that is a baby off of someone else's so you might want to look on some local reef forums to see if anyone has had an anemone split lately and they're willing to sell.
DO NOT buy an anemone that has been kept high up on the rocks under MH lighting, it will die in your tank. Try to find someone (whether a local reefer or LFS) that has kept the anemone further away from the light or under PC or T5 lights, this will greatly improve your success rate. DO NOT buy an anemone online, you need to see it and know what you're getting. You need to know what kind of water parameters and light parameters its been kept under.