Here's what Puddles is referring to: "Adding some pussy willow bark to the aquarium also helps in the fight against infection, due to its natural antibiotic content it makes it a great natural treatment. The pussy willow bark should not be used long term though, due to its antibiotic content it also has the ability to start killing off the good bacteria in the aquarium, so 3 days maximum is recommended."
I've never done it, so I don't know anything about it.