Australian Sea Apple Question
 

I have an Australian Sea Apple in a 80gal tank, that I received from a friend, for a little over 1 year now. It has been doing well but over the last few days, it descended to the bottom of the tank underneath a lot of rock. Should I be worried or bring it back up closer to the light?

Also, I've read that it can grow up to 7 inches. But over the past year, it remains around 2-1/2 inches. Does anyone have experience in raising the sea apple? Like the best type of food for it?

Thanks. Any thoughts are greatly appreciated!