Gemmy, you can hijack my threads anytime, I think I do it all the time, to be honest i really don't understand this whole hijacking thread thing, if you have something relevent to say, then hijack away. I have been reading up on clams a bit, derasa yes substrate but they are the largest between the crocea and derasa, they can get up to 24" in the wild. Crocea are much smaller and prefer to attach to rock, size 6". Maxima 12" in the wild.