You really need to use Focus to bind it to the food. It is completely ineffective for internal parasites dosed to the water column. You need to get the a high enough dose inside the fish. You just can't do that through the water column.
While it is "Safe" it can harm inverts in the water column if you follow the dosing instructions.
If you need I make a prepared frozen food that I use in my QT that is set up with Focus and Metroplex in the correct proportions. It also has Garlic, Selcon, Vitamins and Amino Acids. I was not prepared to release it for sale, yet, but It is coming soon. I could get you some.
I get EVERY fish I QT to eat this food eventually.