Get some frozen krill. Break a small piece off & Thaw it in tank water with Selcon added. Once thawed touch a piece to their tentacles & they'll feed themselves. They seem small now but those 2 little ones have hardly ever been fed. The smallest one has never been fed directly. If you want it to grow feed it good once or twice a week. If you want it to stay small feed it sparingly.
They will move around until they find a place they like with the right ammount of light, the right ammount of current & a place to hide their foot for protection. Then they'll hang there in that spot until the light, current or feeding changes.