Peroxide will react with a lot more than just blood, so even if it foams it might not be due to blood. I bet it was the watermelon. Feed them beets and see what happens..... 

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but if you get no reaction, then you possibly could rule out blood.. ??Peroxide will react with a lot more than just blood, so even if it foams it might not be due to blood. I bet it was the watermelon. Feed them beets and see what happens.....![]()