probably something I shouldn't post only because I'm a firm believer that clams need MH's to thrive. Here's a picture of a Crocea I had up high in my old 55 using 4x55 watt PC's and 4x40 watt Actinics.
If you look hard you'll see GSP on one side and some trimmed Xenia on the other. Its been awhile but I'd say this clam was in this tank for at least a year until I moved it to my 150. http://hometown.aol.com/golfish49/images/crocea.jpg