You may want to slow down and do some research before someone sells you aptasia... There are some pretty big differences between species of anemones that will make some completely unsuitable for your tank. Read up on how large they can get, what will or wont host in them, what their requirements are for lighting etc. Then decide if your tank is ready for one and what type you could get.
Here is a great article to get you started
http://www.carlosreef.com/download/fclick.php?1