FarmHub
8.6 Common Fish Diseases and Their Treatment
Parasites 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.
· Kentucky State University8.5 Disease Problems and Management
Fish Disease and Treatment Fish culture is inherently a messy business. Bacterial pathogens and parasites that affect fish are naturally occurring and opportunistic by nature. Good management, proper husbandry practices, and daily observation of fish can prevent many issues associated with fish health. Proper management techniques in the fish production of the aquaponics system should include: system design, water quality monitoring and correction, equipment maintenance, feed storage, fish observation to remove sick or dead fish, and worker sanitation.
· Kentucky State University8.4 Common Pests
Mites: Mites are a very common pest, affecting hundreds of plants. These small arthropods are very small, often measuring less than 1 mm in length, and have sucking mouthparts. Damage to plants by mites includes brown stippling on leaves, upturned leaf margins, stunted plant growth, and webbing between plant structures (spider mites). Symptoms can mimic those of viral infections, particularly those caused by the broad mite, so identification should be done under a microscope.
· Kentucky State University8.3 Chemical Applications
Pesticides derived from biological or microbial sources are also effective and widely available. Biopesticides are derived from natural materials such as animals, plants, bacterial, and certain minerals. Common biopesticides include biofungicides (Trichoderma), bioherbicides (Phytopthora), and bioinsecticides (Bacillus thuringiensis, B. sphaericus). B. thuringiensis (Bt) has become an increasingly common mechanism to target specific vegetable pests. Bt consists of a spore that contains a toxic protein crystal. Certain insects that consume the bacteria release toxic crystals into their gut, blocking the system, which protects the pest’s stomach from its own digestive juices.
· Kentucky State University8.2 Biological/Chemical Controls
IPM strategies can also incorporate biological and/or microbial controls. These controls have many ecological advantages, including their host specificity, environmental beneficence, ability to be used in conjunction with chemical application, and that they are nontoxic and nonpathogenic to wildlife, humans, and other organisms not closely related to the target pest. Considering that these are precise, targeted control measures, cost can often be substantial. Biological controls utilize insect predators of the target pest to control population numbers.
· Kentucky State University8.1 Physical Controls
Preventing insects from entering the greenhouse is the best pest management strategy for aquaponics. Prevention is accomplished through consistent monitoring and physical controls. The use of adhesive, pheromone, or light traps can be used to monitor type of insect and level of infestation. Screens can be an effective physical control and can be used on outdoor systems or to cover vents in a greenhouse. Mesh size is an important consideration and should be as small as possible without restricting air flow and ventilation.
· Kentucky State University7.2 Common Nutrient Deficiencies
A skill that is beneficial for aquaponics producers to keep in their toolbox is the ability to visually diagnose nutrient deficiencies. Once a plant exhibits symptom of a deficiency, severe stress is already occurring. Early detection and diagnosis are important. Process of elimination can help growers successfully identify a nutrient deficiency. Key factors include recognizing where it occurs in the plant (mobile or immobile nutrient); taking note of the general appearance, such as color pattern or overall appearance; and eliminating other factors that may be causing the issue, such as light or heat damage.
· Kentucky State University7.1 Providing and Measuring Plant Nutrients
Nutrients enter the aquaponic system in the fish feed. The amount of nitrogen that is available to the plant is directly related to the protein content of the feed. The higher the protein content, the more nitrogen is available for plant growth. Unfortunately, high protein feeds are very expensive, so feeding a higher protein feed than your culture species requires is cost prohibitive. Nitrogen comes from the breakdown of proteins, whose structural components are made up of nitrogen-rich amino acids.
· Kentucky State University6.7 Corrective Measures
Low dissolved oxygen (below 5 mg/L): increase aeration, reduce feeding until corrected Low pH (below 6.0): add base (calcium hydroxide, calcium carbonate, potassium hydroxide or potassium carbonate), reduce feeding until corrected High ammonia (above 1 mg/L TAN): reduce feeding until corrected, perform 20% water exchange, check for accumulated solids, increase biological filtration High nitrite (above 0.5 mg/L): reduce feeding until corrected, perform 20% water exchange, increase biological filtration Consistently high nitrate: reduce fish biomass or feeding rate, add more plant biomass
· Kentucky State University6.6 Cycling the System
Cycling refers to the process of establishing the biological filter. This can take between six to eight weeks (Figure 17). Nitrifying bacteria are found naturally in the environment, so the process begins by adding a source of ammonia. This can be accomplished through adding fish, fish food, or water from a well-established system, or a combination of these. One of the most common mistakes when using fish to cycle a system is adding too many fish initially.
· Kentucky State University