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If fish stocked into production become sick, they should be removed from the system immediately for treatment or disposal. Water amendments should be made promptly, stocking rates should be checked, water flow should be checked, and water exchanges may be necessary. There are no good treatment options for treating systemically in production, as chemicals cannot be used with coupled aquaponic systems. Fish can be removed or isolated, treated in containment, and reintroduced at a later date.
System design plays a role in disease prevention. Tanks used for fish culture should be round and preferably have a conical bottom for removal of settle-able solids. Design should be such that tanks are easy to disinfect, can be isolated individually from the rest of the system, and have windows to view fish in the water column.
Ich (white spot disease): Ich is caused by the parasite Ichthyophthirius multifiliis (Ich). Ich appears on infected fish as small white specks on their skin and/or gills (Figure 21a). Fish may exhibit “flashing” behavior, characterized by a quick rubbing or scratching movements against the tank bottom, wall, or surface of the water (Durborow et al. 2000). Excess mucus is commonly present; however, the only clear sign may be a dead or dying fish. Treatment for Ich is difficult; however, elevating water temperature to above 85circF can kill Ich by disrupting its life cycle. Chemical treatments for quarantine tanks or decoupled systems include multiple treatments of formalin, copper sulfate (CuSO4), or potassium permanganate (KMnO4). Check appropriate dose rates before administering. These chemicals should not come into contact with plant components and must be administered in an isolated tank. Simply harvesting the fish may be the simplest solution.
Whirling disease: Caused by Myxobolus cerebralis, whirling disease primarily infects salmonids (trout and salmon) and can enter the aquaculture system through affected fish. Symptoms include abnormal swimming, darkening of posterior part, and skeletal deformation (Idowu et al. 2017). There is no true effective treatment for whirling disease. Producers should only purchase salmonid fingerling from hatchery that are certified whirling disease free and use treated water or ground water for production.
Columnaris: Infections from Flavobacterium columnare are common in aquaculture-reared fish. Common symptoms include red or pale ulcers on the skin; yellowish mucus on