Bacterial

Columnaris / Fin Rot / Saddleback (Flavobacterium columnare)

Symptoms:

Frayed fins, falling apart
Whitish spots on the body (they are not pimples like ich)
Grayish lesions on the back (saddleback)
Death within 24–72 hours in acute cases Cause: Aerobic bacteria; occurs due to stress and poor water quality Treatment:
Antibiotics: Kanamycin, Erythromycin (Maracyn), Co-trimoxazole
Rock salt (1–2 g/L) in fresh water as an adjuvant
Improving Water Quality

Aeromonas (Aeromonas hydrophila / salmonicida) — Bacterial rot

Symptoms: Skin ulcers, bleeding, raised scales (hydrops), necrotic gills Cause: Opportunistic bacteria → occurs in stressed fish, dirty water, or following parasitic infections Treatment:

Oral antibiotic (kanamycin, ciprofloxacin in medicated feed)
Bath treatment (when administered externally)
Drastically Improve Water Quality

Head-and-Lateral-Line Erosion (HLLE)

Symptoms: Crater-like lesions on the head and lateral line, primarily in discus, oscarfish, and Acanthurus Cause: Still under debate — likely nutritional deficiency (vitamin C, minerals) + water quality + Hexamita (intestinal parasite) Treatment:

Improve diet (vegetables, vitamins)
Improving Water Quality
Metronidazole (if Hexamita is present)

Mycobacteriosis (Mycobacterium marinum / fortuitum)

Symptoms: Chronic weight loss, internal damage, pallor, curved spine (scoliosis) Cause: Intracellular bacteria, highly resistant Zoonosis: It can infect humans through open wounds (swimming pool granuloma). Wear gloves. Treatment: Very difficult; practically incurable. Humanely euthanize the affected fish. Disinfect the aquarium.

FUNGAL DISEASES

Saprolegnia (Saprolegniasis)

Symptoms: Cotton-like white or grayish filaments on wounds, unfertilized eggs, weakened fish Cause: Water mold (aquatic fungus), opportunistic Treatment:

Malachite green (highly effective)
Rock salt (1–3 g/L) — not for fish sensitive to salt
Improve overall conditions

VIRAL DISEASES

Lymphocystis

Symptoms: White nodules resembling cauliflower florets on the fins and skin Cause: Iridovirus Treatment: No treatment. Most cases resolve on their own within weeks or months. Not fatal. Isolate to prevent spread. Avoid stress.

Gurami Iridovirus (DGIV)

Symptoms: Lethargy, swelling, death within days Affects: Primarily Trichogaster lalius (dwarf gourami) Treatment: No treatment. Only buy from trusted suppliers; avoid products imported from Asia (high prevalence).

Neon Syndrome (Pleistophora hyphessobryconis)

Symptoms: Faded or whitish blue/red coloration, erratic swimming, curved body Cause: Microsporidium (fungal parasite)