In some cases, the fish are also receiving injections, and an additional source of antimicrobial activity is desired. These are some reasons medicated foods are chosen. Not to mention that giving medicated foods is simple as can be. Many people prefer medicated foods because they find it effective and simple. The only problem has been that the sickest fish will not usually eat, so we see that medicated foods are helpful only in fish which can be tempted to try it.
Medicated foods made with top dressing technology are the least effective.
The reasons include that the antibiotics are on the surface of the food in an oil mix. What a bummer. Medicated foods with the antibiotics milled in are ideal. They can float or sink, and the antimicrobial activity remains in the food until it is eaten. When your fish are sick with a bacterial infection, or weak and stressed from their long winter fast, it is very important that an antibiotic be administered.