corys being murdered

Aug 11, 2017
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I have a 4' planted tank with 6 medium angels, 20 cardinals, and six corys. All was well until I added two pairs of swordtails. Now every morning I find a dead cory with a few bites taken out of him. The angels are a bit aggressive, nipping at one another, and the swords seem peaceful, but the killings began only after the swords arrived. I heard swordtails are mostly vegetarian. I feed them all pellets, flakes, and freeze-dried tubifex. Any idea who the culprit might be? Would live food curb the blood lust?