Methods and devices for removing non-viable tissue at a treatment situs are described. The method can include administering a selective biofilm stain dye to the treatment situs at a dilution that selectively stains non-viable tissue compared to viable tissue at a selectivity ratio that provides a visually identifiable separation between the non-viable tissue and the viable tissue. The selective biofilm stain dye is diluted in water to a concentration of from about 0.001 mg/mL to about 0.5 mg/mL. The method can also include visually identifying the non-viable tissue, and removing the non-viable tissue based on the visual identification.

A biofilm staining device can include an applicator having a dispense tip, a rupture lever adapted to rupture a rupturable capsule and release a selective biofilm stain dye, and a housing sized to retain the rupturable capsule and adapted to allow released selective biofilm stain dye to flow to the dispense tip.