actually, crocea do better on rocks from my understanding. Derasas prefer on the sand bed. even if it had not gotten enough light in the tank, a few days is not going to do one in. I'm inclined to say it had either a predator or some sort of disease or something. Post it up over at www.clamsdirect.com and someone might be able to help you there since they specialize in clams. Were you feeding it directly? THat can "suffocate" one. I haven't fed my derasa since i got it in September and it has grown in that time and is doing well under MH.
I'm also sorry to hear about the loss of the clam.
I'm also sorry to hear about the loss of the clam.
