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the skin, gills, and/or mouth; and necrosis/erosion of the gills. Saddleback is a common lesion caused by columnaris and appears as a pale white saddle-like band encircling the body (Figure 21b). The bacteria can cause disease under normal culture conditions, but more likely when fish are stressed by low oxygen, high ammonia, high nitrite, high water temperatures, rough handling, mechanical injury, and crowding. (Durborow et al. 1998). Columnaris is typically treated with chemical treatment of the water using KMnO₄ or by using Terramycin® (oxytetracycline HCl). Medicated feed that contains the antibiotics Aquaflor®, Terramycin® or Romet® may be effective. Chemical treatments or antibiotic feed should not come into contact with plant components and must be administered in an isolated tank.

Aeromonas: Aeromonas is a genus of bacteria that is widespread and is commonly isolated from freshwater culture environments. The disease caused by these bacteria in fish is called Motile Aeromonas Septicemia (MAS) (Hanson et al. 2019). Aeromonas infections are probably the most common bacterial disease diagnosed in cultured warmwater fish. Fish with septicemia often have hemorrhages (red areas or spots) on the skin, eyes, and fins; a dis-tended abdomen; flared scales due to edema in the scale pockets (dropsy); and/or a red, inflamed anus (Figure 21c). Internally, the muscle and visceral tissue are often red, and the body cavity may contain bloody fluid. Typical MAS can be attributed to a predisposing factor, such as a handling event, temperature shock, water quality stressor, spawning, or aggression. Treatment is currently limited to three antibiotics: Aquaflor®, Terramycin® and Romet®-30. Proper withdrawal times for each antibiotic must be observed before treated fish can be processed/harvested. Chemical treatments or antibiotic feed should not come into contact with plant components and must be administered in an isolated tank.

Enteric Septicemia of Catfish (ESC): ESC is also known as “Hole-in-Head Disease” and is caused by the bacteria Edwardsiella ictaluri. It most commonly affects catfish species and is accountable for one-third of reported fish diseases in the southeastern U.S. Behavioral signs of infection include head-chasing-tail or whirling rather than swimming, as well as “star gazing.” External signs include red or white shallow ulcers, a hole appearing in the top of the head, and fluid buildup in the abdomen, causing severe distension. Treatment is typically administering medicated feed containing the antibiotics Aquaflor®, Romet®, or Terramycin®. Chemical treatments or antibiotic feed should not come into contact with plant components and must be administered in an isolated tank.

Tilapia Lake Virus (TiLV): TiLV is one of the only significant viruses that affect tilapia in both wild and cultured situations. It is caused by Tilapia tilapine virus and has been seen in Asia, Africa, and South America. It is transferred quickly through infected populations, and there is no treatment at the time of this publication.

Plant disease problems can be difficult and time consuming to treat. Preventing issues from arising is the first step in proper plant care. Many foliar plant diseases are present during conditions of high temperature and humidity. Providing proper ventilation and reducing humidity will prevent conditions that allow mold and disease to spread to other plants.

Plant nutrition plays a direct role in disease resistance in plants (Agrios 2005). Providing the correct balance of nutrients is important not only for growth but also to decrease susceptibility and increase recovery from certain plant disease. Table 10 describes the role of certain nutrients for prevention of plant disease. Below are common plant diseases in aquaponic systems.