To catch a killer

[Tie Sun Also Rises]

Last week i noticed something is eating my Xenia and Lollypop corals. Both have been almost completely eat'n alive. This morning at dawn i noticed a white mass at the base of the xenia excreating what looked like spores and a white paste substance. Once the lights came on it disappeared. I can't tell what has NOT been eat'n these corals; its not a fish or crab. I bought a bristol worm trap last night and caught two little critters, i'll use the trap tonight, but i'm concerned that the lollypop and zenia won't make it through another night. Any advice? Can i place these two peices into a bucket at night till i catch the killer?