Fish and other aquatic animals have a remarkable immune system and body architecture to fend off diseases. Yet even with great design, illness sometimes happen. These tables are some of the more common freshwater pathogens an aquarist will find affecting their aquarium.
For more detail on any pathogen click on the name of the pathogen found under each picture.
Common health problems
| Image | Common name | Scientific name | Disease name | Life cycle | Transmission | Symptoms | Treatment | Temp | Prognosis | Prevention |
|---|---|---|---|---|---|---|---|---|---|---|
 Profile Disease Ich | Ich | Ichthyophthirius multifiliis | White Spot | Multi stage: theront, trophont | Direct & indirect contact | white spots | water temp, formalin, copper sulfate | 82 - 86 F | Treatable | Biosecurity and Quarantine |
 Profile Disease Dactylogyrus | Dactylogyrus | monogenean trematodes | Gill flukes | Single host | Direct & indirect contact by larvae | rapid respiratory, pale gill, lethargy, reduced appetite | chemical, salt bath | none specified | Treatable | Biosecurity and Quarantine |
 Profile Disease Velvet | Oodinium | Oodinium pillularis | Velvet, Gold Dust Disease | Multi stage: trophont tomont | Direct contact and contaminated water | Golden coating, rapid respiratory, clamped fins, flashing, lethargy | water temp, malachite green, copper sulfate | 82 - 86 F | Treatable | Biosecurity and Quarantine |
 Profile Disease Hexamita | Hexamita | Hexamita inflata | Hexamitiasis | Multi stage: trophozoite stage, Cyst stage | Ingestion of contaminated water | Pits & legions on the head, eyes and lateral line of fish. Can appear as open wounds | metronidazole, antiprotozoal medications | infections occur in warmer water, maintain 75-82 F | treatable with early detection | Biosecurity and Quarantine |
| Image | Common name | Bacteria name | Disease name | Life cycle | Transmission | Symptoms | Treatment | Temp | Prognosis | Prevention |
|---|---|---|---|---|---|---|---|---|---|---|
 Profile Disease Fin Rot | Fin Rot | Aeromonas hydrophila, Pseudomonas aeruginosa | Fin rot | Bacterial free living opportunistic pathogen | Direct contact, contaminated water | Fraying or shredding of the fin edges, lethargy, lost appetite | Antibiotics: fluoroquinolones and aminoglycosides | Resilient at most water temps | Treatable: note the bacteria is part of normal microbiota of fish | Adjust water chemistry to proper levels, check filtration, water exchange |
 Profile Disease Aeromonas & Pseudomonas | Aeromonas and Pseudomonas | Aeromonas hydrophila, Pseudomonas aeruginosa | Gram-negative bacteria of Pseudomonadaceae | Bacterial free living opportunistic pathogen | Direct contact, contaminated water | Skin lesions, Ulcers, Hemorrhages, lethargy, appetite loss, swimming difficulty | Antibiotics: fluoroquinolones and aminoglycosides | Resilient at most water temps | Treatable: note the bacteria is part of normal microbiota of fish | Adjust water chemistry to proper levels, check filtration, water exchange |
 Profile Disease Columnaris | Cotton wool | Flavobacterium columnare | Columnaris | Bacterial free living opportunistic pathogen | Vector: open wounds, mucous membranes | White fuzzy patches, ulcerations, lesions, fin rot, lethargy, appetite loss, swimming difficulty. Co-infection often present. | Antibiotics: erythromycin and oxytetracycline. Salt bath | Resilient at most water temps. Thrives in 77-86 F | Treatable: note the bacteria is part of normal microbiota of fish | Adjust water chemistry to proper levels, check filtration, water exchange |
 Profile Disease Hemorrhagic Septicemia | Hemorrhagic septicemia | Pasteurella multocida, gram negative | Hemorrhagic septicemia | Systemic infection | Direct contact, contaminated water or food,, fomite contact. Carrier can shed bacteria without symptoms | lethargy, apettite loss, internal and external bleeding through ulcers | Antibiotics: Florfenicol, Sulfadimethoxine/Ormetoprim, Trimethoprim-Sulfamethoxazole | non-specific | Treatable: | Adjust water chemistry to proper levels, check filtration, water exchange. exercise bio-security protocols |
| Image | Common name | Scientific name | Disease name | Life cycle | Transmission | Symptoms | Treatment | Temp | Prognosis | Prevention |
|---|---|---|---|---|---|---|---|---|---|---|
 Profile Disease Lymphocystis | Lymphocystis | Lymphocystivirus, part of Iridoviridae family | Lymphocystis | Virus invaded cells will shed virons to water, highly contagious | Direct contact with infected fish or contaminated water, highly contagious | Raised cauliflower-like growths or nodules on skin or fins | Lymphocystis growths will eventually regress | Highly resilient will tolerate wide range of temps | Virus will resolve itself and remain dormant, may reappear in stressful conditions | Bio-security practices, isolate visibly infected fish |
| Image | Common name | Scientific name | Disease name | Life cycle | Transmission | Symptoms | Treatment | Temp | Prognosis | Prevention |
|---|---|---|---|---|---|---|---|---|---|---|
 Dropsy | Dropsy | Dropsy | pinecone disease | Secondary condition | non-contagious | Lethargy, appetite loss, pale skin, bulging eyes, clamped fins, rapid or labored breathing | Treating dropsy involves addressing the underlying cause rather than the symptom itself | non-specific | Often fatal | Maintain a healthy aquarium |
 Swim Bladder | Swim Bladder | Swim Bladder | Swim Bladder Disease | non-specific | non-contagious | Floating, sinking, inverted swimming, difficulty swimming, appetite loss | Address underlying cause, for constipation - fast 1-2 days, bacteriological - consult vetrinarian for antobiotics, | non-specific | Treatable | balanced diet, avoid overfeeding, maintain good water chemistry |
 Popeye | PopEye | PopEye | exophthalmia | Multi stage: trophont tomont | non-contagious | Protrusion or bulging of one or both eyes from eye sockets. | Treatment is specific to underlying condition: antibiotics, water chemistry, balanced diet | non-specific | Treatable | balanced diet, avoid overfeeding, maintain good water chemistry |
Fungal Infections: Infections caused by fungal organisms that often appear as cotton-like growth on the fish’s body or fins. Fungal infections can occur as secondary infections in wounds or due to poor water conditions.
Ammonia/Nitrite Poisoning: Toxicity caused by high levels of ammonia or nitrites in the water. It can occur due to poor water quality, overfeeding, or inadequate filtration. Symptoms may include lethargy, gasping at the water surface, and reddened gills.
Parasitic Worms: Betta fish can be affected by internal or external parasitic worms, which can cause various symptoms, including weight loss, reduced appetite, and deterioration of overall health.
Ulcers and Open Sores: Bacterial infections that result in open wounds or sores on the fish’s body. These wounds can become infected and lead to further health complications if left untreated.
Tumors: Abnormal growths that can be benign or malignant. Tumors can affect various parts of the fish’s body and may cause physical deformities, changes in behavior, and overall decline in health.
Saprolegnia (fungus-like pathogen): Saprolegnia infections, known as saprolegniasis or water mold disease, primarily affect aquatic animals such as fish and amphibians. Infected individuals often display visible cotton-like or fuzzy white growths on their skin, fins, gills, or eggs.