Within an aquaponics system is a delicate ecosystem composed of fish, bacteria, and plants. For everything to work perfectly, each part of the system must be balanced and healthy. Fish are required to be healthy to produce ammonia that is converted by the bacteria into nutrients for the plants. If the fish is not healthy, waste production slows, resulting in an imbalance system, where the bacteria is not enough for the plants.
So it is important that fish diseases are recognized and treated correctly to ensure a balanced system. Fish diseases in aquaponics are always the result of abiotic and biotic factors. Abiotic are non-living chemical factors that affect toxicity or water quality. Biotic factors are living pathogens or organisms that can directly or indirectly affect their environment. To help you identify and accordingly act on your fish health issues, here is the list of causes and symptoms of common fish diseases of aquaponics fish.
Abiotic Fish Diseases
Hypoxia
Causes:
- insufficient aeration
- fish overcrowding
- low water flow
- reduced dissolved oxygen
- increased temperature or salinity.
Symptoms:
- fish gathering at water inflow
- fish piping
- Depression
- larger fish die while smaller fish alive
- dead fish with an operculum and widely open mouth.
Treatment:
- restore or add aeration
- reduce stocking density
- reduce feeding
- monitor ammonia and nitrite levels
Temperature Stress
Causes:
- lack of heating or insulation
- improper management
Symptoms:
- lethargy
- mould disease (hypothermia)
- dyspnea (hyperthermia)
Treatment:
- insulate the fish tank
- add a water heater
- shade the tank
- ventilate at night
- use a cooling system
- use a greenhouse in cold seasons
Ammonia Poisoning
Causes:
- new tank syndrome
- biofilter failure (several reasons, also for antibiotic or antiseptic treatments for fish if carried in aquaponics tank)
- recently cleaned biofilter media
- overcrowding in the tank
- Overfeeding
- excessive protein in feed
- reduced water flow,
- reduced oxygen in water
- temperature drop inhibiting nitrifying bacteria.
Symptoms:
- abnormal swimming
- not eating during feeding
- darker gills
- larger gills (hyperplasia for chronic toxicity)
- redness around eyes and fins.
Treatment:
- immediate (20-50%) water exchange
- reduce pH with acid buffer
- add biofilter media
- improve oxygenation
- adjust temperatures
- stop feeding
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Nitrite Poisoning
Causes:
- new tank syndrome
- biofilter failure
- biofilter media recently washed/cleaned
- overcrowding in the tank
- overfeeding, excessive protein in feed
- reduced water flow
- temperature drop.
Symptoms:
- breathing difficulty
- darker gills
- brownish blood
- abnormal swimming
- gathering near the water's surface
- Lethargy
- redness around eyes and fins.
Treatments:
- immediate (20-50%) water replacement
- add biofilter media
- reduce fish density
- stop feeding
- add chloride
- improve aeration
- adjust the temperature
- avoid fish disturbance
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Hydrogen Sulphide Toxicity
Causes:
- accumulation of solid waste with anaerobic conditions
- lack of aeration
- increase of temperature
Symptoms:
- the smell of rotten eggs
- purple-violet gills
- unusual swimming behavior (fish beginning to swim sideways)
- Reduced appetite
- Develop irreversible gill damage
Treatments:
- removal of organic wastes accumulated in anaerobic conditions
- transfer fish into a recovery tank until the cause is removed
- increase dissolved oxygen in water
- increase pH
- lower the temperature
pH
Causes:
low pH:
- low buffer in water
- improper addition of acid
High pH:
- improper buffer addition
- water too rich in hardness/alkalinity, too much carbonate in biofilter media
Symptoms:
low pH:
- acute death with trembling and hyperactivity,
- difficulty in breathing
- increased mucus production
High pH:
- opacity in skin and gills
- corneal damage
Treatment:
- replacement of water
- buffer addition
- adding of base or acid to adjust pH
- in low pH: adjust with base only if the ammonia level is very low
- in high pH: add rainwater or distilled water
Improper Salinity
Causes:
- salinity concentrations beyond fish tolerance
- water replacement with sources with higher/lower salinity
- miscalculation of salt addition
- evaporative loss causing higher salt concentrations in the remaining water
Symptoms:
Treatment:
- adding rainwater or freshwater to decrease salinity
- adding salt to increase salinity (addition of salt should not exceed 1 mg/liter increment per hour)
Gas Bubble Disease (Gas Supersaturation)
Causes:
- rapid increase of temperature
- rapid water pressure decrease that reduces the gas solubility
- use of groundwater
- excess water oxygenation
Symptoms:
- fish floating to the surface
- popped eye
- Small bubbles near or in the fins, gills and eyes
- presence of emboli in the blood and any organs
Treatment:
- reduce the excess gas
- avoid stress
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Food Deficiency
Causes:
- food lacking in essential elements
- improper feed storage
- lack of feed variance
- low feed ration
- excessive fat accumulation
Symptoms:
- poor growth
- depression
- mortality
- anemia
- ocular lesion
Treatment:
- follow fish feed requirements
- add variety to the diet
- provide specific pellet fish feed
- provide vitamins and minerals
- provide balanced fish feed
Bacterial Diseases
Columnaris
Causes:
- main agent Flexibacter columnaris
- concurrent causes of acute stress
- increased temperatures
- low oxygen
Symptoms:
- reddening and erosion of skin turning into shallow ulcers and necrosis
- necrosis of gills
- the release of yellowish mucus from the lesions
Treatment:
- prolonged immersion in potassium permanganate to treat fish initially and increase appetite to let them eat medicated feed
- immersion in copper sulfate
- antibiotic treatment (oxytetracycline,nifurpirinol) in a separate tank eliminates the underlying causes
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Dropsy
Causes:
- various bacteria
- Parasites and viruses
- concurrent causes also weakened fish and inadequate water standards
Symptoms:
- infection of the internal organs leading to fluid accumulation in the body
- bloated fish
Treatment:
- feeding fish with medicated feed containing antibiotics (chloramphenicol, tetracycline) in a separate tank
- elimination of water or environmental causes
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Fin Rot
Causes:
- bacterial infection from different agents
- poor water conditions
- bullying from other fish,
Symptoms:
- damaged fin ray exposed
- loss of color
- Bleeding
- ulceration
Treatment:
- identify the causes
- treat the fish in a separate tank and provide medicated fish food with antibiotics (chloramphenicol or tetracycline) or dissolve the antibiotic directly in the water
- keep sick fish separate until fully recovered
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Streptococcosis
Causes:
Symptoms:
- acute hemorrhages on the body
- popped eyes
- sanguineous liquid in the peritoneal cavity
Treatment:
- treatment with antibiotics (oxytetracycline, ampicillin) in a separate tank
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Tuberculosis
Causes:
- Mycobacterium bacteria
- Overcrowding
- poor water quality
Symptoms:
- emaciation
- Lethargy
- lack of appetite
- hollow belly
- skin ulcers
- loss of scale and fin erosion
- the appearance of yellow or dark tubercles on the body, presence of 1-4 mm white nodules in the internal organs (kidney and spleen)
Treatment:
- treatment with erythromycin
- Streptomycin and vitamin B-6 or elimination of fish (attention is required when handling as the disease may be transmitted to humans)
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Fungal Diseases
White Cotton Saprolegnia
Causes:
- Saprolegnia app.
- often as an opportunistic agent following other infections and overall fish weakness
- concurrent causes of acute stress
- temperature drop
- transport stress
Symptoms:
- white, brown, or red, cotton ish growth on the fish surface
- ocular lesions as cloudy eyes causing blindness and loss of the organ
Treatment:
- prolonged salt or formalin bath
- treatment of eggs with hydrogen peroxide, or prolonged immersion in methylene blue
- lesions may be treated with a cloth soaked with povidone-iodine
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Protozoan Diseases
Hexamitosis (Hole in The Head Disease)
Causes:
- Hexamita spp.
- Spironucleus spp
- flagellate protozoa attaching the intestinal trait
- it affects debilitated and stressed animals
Symptoms:
- occurrence of the parasite in the intestine and gallbladder or other organs in more advanced cases
- presence of abdominal distension and white mucous excrements followed by behavioral disorders such as fish hiding in corners with head down and swimming backward, progressive reduction of head volume above the eyes, and darkening of body
Treatments:
- use of Metronidazole both in the feed (1%) and in the water (12 mg/liter)
- addition of magnesium sulfate as a cathartic
- increase temperature and improve environmental conditions
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Ich/white spot
Causes:
- Ichthyophthirius multifiliis
Symptoms:
- small white cysts (up to 1 mm) covering the fish's body
- giving an appearance of salt grains that emerge
- mucous skin
- skin erosions
- behavioral disorders are seen as lethargy
- loss of appetite
- body rubbing against walls in the attempt to remove the parasite
Treatments:
- the parasite is susceptible to treatment during the free-swimming stage of juveniles following the adult stage on the fish and the production of cysts that fall on the bottom
- treatment with a salt bath or formalin bath every week until cured
- maintain the water temperature above 30 °C for ten days
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Trichodina
Causes:
- a saucer-shaped protozoan parasite that attaches to gills and the body surface of the host fish
- often found in poor water quality and overstocking
Symptoms:
- a wet mount (microscopy) of skin scraping will show the parasite
- a grey film on skin and gills
- along with an excess of white mucous secretion
- anorexia and loss of condition in heavily infected fish
Treatments:
- formalin or potassium permanganate bath
- salt or acetic acid bath immersion (freshwater protozoa only)
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Velvet/Dust
Causes:
- piscinoodinium dpp
- a parasitic skin flagellate that binds to the host
Symptoms:
- brownish dust covering the body or the fins
- respiratory discomfort (out-of-breath) with a quick movement of the gill due to the presence of parasites on the gills
- cloudy eyes
- formation of cysts that discharge free infective parasites
Treatments:
- this disease is highly contagious and fatal
- raising the temperature to 24-27 °C will speed up the cycle of treatments
- leaving the system without fish for two weeks to remove the protozoan
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Parasitic Diseases
Anchor Worm
Causes:
- copepods of various origins
- introduced from the wild
Symptoms:
- parasites on the skin, gill, mouth, erosion, and ulceration
- red spots on the skin that can rise to 5mm
Treatments:
- can be identified with a magnifying lens
- extended treatment with salt
- hydrogen peroxide
- formalin, and ivermectin are the remedy for lice
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Flukes
Causes:
- flatworms (about 1mm long) infesting gills and skin
- detectable with a magnifying lens
Symptoms:
- scraping on the tank walls
- release of mucus from the gills
- fast movements, damage of the gills and fins
- Paleness
- quick respiration
- flopping of pins.
Treatments:
- 10 to 30-minute bath in 10 mg/liter of potassium permanganate in a separate tank (for freshwater parasites only)
- salt, formalin or copper bath
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Leeches
Causes:
- external parasites usually introduced from the wilds.
Symptoms:
- the presence of parasites on the skin with red or white lesions.
Treatments:
- avoid the introduction of raw plants or snails
- salt bath
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Nematoda
Causes:
- threadworms infesting the body, but only visible when they concentrate on the anus
- infestation usually occurs with the introduction of wild or fish ponds
Symptoms:
- loss of weight
- lethargy void bellies
- accumulation of parasites around the anus
- worms in the intestine
Treatment:
- feed medicated with fenbendazole oral levamisole oral
Conclusion
Fish diseases are sometimes unavoidable in aquaponics, but you can immediately take the right action if you know its causes, symptoms, and treatments. However, if you want to prevent fish diseases, you should properly take care of your fish. One way to do this is to have routine management practices that will help keep your fish healthy and happy. To prevent fish diseases from affecting your aquaponics system, here are the few things you can do:
- Only purchase fish from a reliable facility.
- Feed your fish with a healthy and balanced diet.
- Observe the key water quality parameters.
- Maintain the key parameters at ideal levels at all times.
- Take out uneaten fish feed after feeding.
- Check new fish for any symptoms of diseases and quarantine them for a few days before adding them to your system.
- Provide salt baths to new fish to eliminate parasites and prevent infections.
- Store fish feed properly to avoid molding.
- Maintain adequate aeration.
- Keep your fish tank away from direct sunlight.
- Protect your fish tank from snails, birds, rodents, and other animals that can be sources of parasites or pathogens.
Resources:
Food and Agriculture Organization of the United Nations
