This fish food contains OxyTetracycline, which we recommend to treatment Columnaris. Fish infected with Columnaris show a wide range of symptoms and not all symptoms present themselves every time. The most common sign is a milky white coating appears on the skin of the fish (especially Discus) and is often patchy. Fish suffering from Columnaris will usually show at least a little interest in eating. This food is concentrated, so any swallowed will have effective results. Fish with Columnaris will usually have an increased respiration rate and they will often clump together in the corners of the tank. They commonly get darker and will often clamp their fins. Unlike Bacterial Skins Infections after a few days, fish infected with Columnaris will often develop white patchy sores and will have with frayed fins. For use with Ornamental Fish only.