anemone acting strange

I have a green BTA in a 10 gal tank with two other clownfish. this is my first saltwater tank and everything i know about the anemone i learned by asking the store i got it from. ive had it for a couple weeks now and it hasnt picked a spot to settle. sometimes it will pick a spot and act normally for 3 days and then close up and fall off the rock where it lays in the sand face down. when its in the sand it doesnt really drift to find a new spot it will open occasionally in the sand but mostly it just gets flipped upside down so ill go in and flip it back over. since it spends most of its time closed up i have few opportunities to feed it. any help would be great cause im a novice. im not sure if i need to adjust the placement of my powerhead or what i need to do but i really want this thing to act normally