NT Labs Propolis Ref: 110 Description •Cleans and Seals Ulcers •Can be used as a Food Suppliment •Boosts Resistance to Infection A waxy substance produced by bees to protect their hives from infection. Supplied as a thick, dark brown liquid for easier application and lasting protection when fish are introduced back into pond water. NT Labs Koi Care Propolis can be spread over cleaned and dried ulcers and wounds.