Skimmers

[Earthgirl]

Hi there!!
I'm extremely new to this hobby and are just starting out with a 40 gallon cubish tank
I have had it running since last sept. Did the cycle (and coming from fresh, this was much easier!)
How many out there have a skimmer??
I do water changes diligently every 3 weeks or so (depending on the look of the duncan coral... Really good indicator of unhappiness!)
I just bought a red tip bubble aneome which I adore, but want to have the happy and healthy tank that everything deserves
Opinions appreciated!! 