A very sad occurance.... I had a beautiful baby gold Maxima clam shipped to me from a friend in another state, which I carefully acclimated to my tank for a couple of hours. I placed this 1.5" clam on an empty shell in the center of the rockwork in my 55g under MH lighting.
I watched it closely for a few hours, until the lights went out. The next morning when I got up, I checked on the clam, and it was gone from its spot. I saw it on the DSB, covered with Whelks! I've seen these snails in my tank for over a year, and they never caused any trouble with a single thing, so I figured they were good as a part of the clean up crew. Apparently, their favorite meal is clam!!!!!! I quickly pulled the clam out, but it was way too late and only a strip of the mantle was left.
All the whelks I could find have been pulled out of the tank and put in a FO tank or the refugium. The worst part is that I was trusted with this clam, because the previous owner felt I'd take very good care of it. It is heartbreaking when things like this occur. :(