Back in the day, when I first started my marine tank I was very cheap as to my purchases. Not that I don't look for a bargain now, but back then I wasn't sure if anything at all would live. I didn't want to spend $30 or more dollars on something just to have it die. My very first purchase was a small rock with an equally small colony of xenia, specifically pulsing xenia, on it for $9.00. It's called that because the heads pulse in a great rhythmic underwater opera.