When betta fish exhibit symptoms of pop-eye (protruding eyes) and loss of appetite, it is usually associated with bacterial infections, water quality issues, or environmental stress. Comprehensive intervention is required, including improving water quality, isolating and treating the fish, using medications appropriately, and adjusting the environment. Below is a detailed analysis and handling recommendations:
I. Etiology Analysis
Bacterial Infections
Columnaris infection is a common cause of pop-eye, often accompanied by redness and swelling around the eyes and increased mucus secretion. If both eyes are protruding, it may indicate an acute or chronic bacterial infection.
Cloudy eye disease (characterized by white opaque film on the eyes) can lead to blindness within a few days if left untreated, and may even cause death if mold invades the brain.
Water Quality Issues
Aging water, unbalanced pH levels (e.g., highly alkaline environments), and excessive ammonia or nitrite concentrations can irritate the fish’s eyes and weaken its immune system, triggering infections.
Infrequent water changes, insufficient filtration, or residual waste in the tank are the main causes of water deterioration.
Environmental Stress
Sudden changes in water temperature (e.g., a temperature fluctuation exceeding 5°C per hour during water changes in winter) can disrupt the fish’s intraocular pressure, leading to pop-eye.
Poor adaptation to new environments, overcrowded tank conditions, or frequent water changes may weaken the fish’s physical condition, increasing its risk of illness.
II. Treatment Plan
1. Emergency Handling
Isolate the sick fish: Transfer the affected fish to a separate treatment tank to prevent cross-infection.
Improve water quality:
Replace 1/3 to 1/4 of the water daily with aged, temperature-matched new water (water that has been left to stand to dechlorinate).
Add Indian almond leaves (Terminalia arjuna leaves) to regulate water quality and inhibit bacterial growth.
Test and adjust the pH level to 6.5–7.5, and ensure ammonia and nitrite concentrations are close to 0.
Raise water temperature to 30°C: Increasing the temperature enhances the fish’s metabolism and supports the effectiveness of medications.
2. Medication Treatment
Mild Infections
5‰ salt bath: Add 5 grams of sea salt per liter of water, soak the fish for 10–15 minutes, once daily.
Methylene blue bath: Dilute methylene blue according to the product instructions, soak the fish once daily for 3 consecutive days.
Moderate Infections
Oxytetracycline bath: Crush 1 oxytetracycline tablet and dissolve it in 1 liter of water, soak the fish for 40 minutes, once daily for 3 consecutive days.
Hajiebao Eye Repair Agent: Add to the treatment tank according to the product instructions to assist in eye recovery.
Severe Infections
Penicillin or chlortetracycline: Add 10,000–20,000 units of antibiotics per liter of water, while raising the water temperature to 30°C, for 3 consecutive days.
Low-concentration potassium permanganate solution: Sprinkle into the tank or soak the fish (strictly control the dosage to avoid fatal overdosing).
3. Recovery Period Management
Gradual water changes: Replace 1/2 of the water weekly during treatment; replace all water within 2 weeks after treatment ends and rebalance the water quality.
Enhance nutrition: Feed high-protein live food (e.g., bloodworms, nematodes) or high-quality commercial feed to boost the fish’s immunity.
Reduce medication use: Gradually decrease the medication dosage until discontinuation once eye swelling subsides.
III. Preventive Measures
Water Quality Maintenance
Change 1/3 of the water regularly (weekly), clean filter sponges, and keep the water clean.
Install an RO (Reverse Osmosis) system to maintain stable Total Dissolved Solids (TDS) levels.
Environmental Control
Keep the water temperature constant at 25–28°C to avoid sudden fluctuations.
Control tank density: The total length of fish per liter of water should not exceed 1 centimeter.
Nutrition Management
Ensure protein intake is ≥38% during the juvenile stage; add lutein, vitamin A, and calcium regularly.
Avoid feeding a single type of feed; provide a diversified diet of live food and commercial feed.
IV. Precautions
Avoid mixing medications: Antibiotics mixed with glucose may lose effectiveness; strictly follow the recommended medication cycle.
Monitor the fish’s response: If there is no improvement or symptoms worsen within 2 days of medication use, switch to alternative medications promptly.
Hereditary pop-eye: Pop-eye caused by chromosomal abnormalities (e.g., in triploid koi carp) cannot heal on its own and requires environmental adjustments to improve the fish’s condition.