The last time I had a flame scallop about 8 years ago, it would get a chalky substance on the tips of its... its... well, whatever you call 'ems. My guess was that it was sand or waste that was caught up in the mucous from them that built up on the tips of its.... you know.
Also, a little anecdote for you, I honeymooned in Moorea of the Tahitian Islands, and I found a flame scallop under my bungalow deck and when I grabbed it, it swam away from me, and then left the little.... tendrils? on my hand. Kind of weird, they stuck to me like when I've pulled aiptasia out of my system, almost like they had nematocysts. I don't think they do, but I guess it's possible that they trap larger particles of food with their.... tendrils (can anyone tell I'm fishing for someone to tell me what they are properly called?) and then pull them in and eat them, on top of filtering the water.
The end to the story (I was pretty irresponsible, but I wanted to play) was that I fed him to an octopus that was under my bungalow to get him to come out and be friendly with me. Didn't take very long for him to pop out an empty scallop shell.