Focus™ is an antibacterial polymer for internal infections of fish. Focus™ is primarily intended to be mixed with food and/or other medications to make them palatable to fish and greatly reduce the loss of medication to the water through diffusion. For use in freshwater or marine aquaria. When to Use a Medicated Food Mix... Your fish has an internal infection Bloating, abnormal stools, loss of appetite, and weight loss are all signs of a potential internal infection. You are already treating with a medication in the water Sometimes fish will develop several infections at the same time, requiring multiple medications. We don’t recommend dosing two medications into the water, but it is possible to put one medication in the food and the other in the water. There are corals, plants, or invertebrates in the tank Using a medicated food mix will prevent damage to delicate plants or invertebrates from medication. Active ingredients: Active ingredient: polymer bound nitrofurantoin (0.1%)