The story of my first derasa was actually very sad. It was a large beauty of 6" diameter, a bright yellow and orange in color. However, it was one of the animals that was the first to go with a kalkwasser overdosing incident in my 60gal tank. Before that time, it lived happily nestled in the sandbed and never bothered anyone, and just fed on phytoplankton. Like other clams, it should be kept only in tanks with good lighting. After this previous bad experience, I am now working on getting a second one.