i`ve got 3 rounds of ybs and all had it , the brother told me they used to give Virkon `s in the drinker for 2 days , so gave it to my 1st round and 2nd round ,in the mean time had ordered stuff for it from belg , within 4 days the birds appetite was amazing , the 3rd round had the charcoal and it works but not as quick JMO. Vircon s 1 level tea spoon to 1 gallon of water for 2 days don`t worry they don`t drink much of it .