Welcome to the board Jenn. Well, it looks like there are several anenome's in that picture so which one do you mean. When you say rock anenome, to me that means apstasia. They are also called curly Q anenome. Is that it. In the photo I also see feather dusters and at the bottom, an atlantic anenome. Basicly, they eat what ever it is you are feeding your other tank inhabitants. You can use a baster and squirt brine shrimp directly on them. I have also used a product called micro-vert which has worked for me as well.
If it is apstasia, keep in mind that they do multiply fast and can quickly over run your tank. Many people have them and are happy, I myself had one for about 7 months before I finally removed it because it had grown too larg. I think it is a personal choice.
I hope I have helped.
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