i dont think its columnaris...i dont see fungus growth or any lesions onn any of the healthy fish, the pike did eat a few bloodworms today, but still not himself. he can usually eat half a prawn to himself, which actually makes me wonder if he could be choking a a shell i may have missed when i was de-shelling. do you guys think that could be it? but that doesnt explain the tiger becuase they didnt eat prawns at least i cannot recall seeing them do it. Also, could gill flukes be the culprit?