Regarding the issue of betta fish staying at the bottom of the tank, it can be caused by multiple factors. Below are common causes and corresponding solutions:
I. Water Temperature Issues
- Metabolic Slowdown Due to Low Temperature: When water temperature drops below 18°C, a betta’s metabolic rate decreases by 40–60%, leading to bottom-dwelling behavior.
Solution: Use a heater to raise the water temperature to 24–28°C (avoid exceeding 30°C). When changing water, keep the temperature difference within 2°C.
- Temperature Shock: Sudden water temperature changes over 3°C during water changes can cause "stress-induced cold," shown by bottom-dwelling and clamped fins.
Solution: Preheat new water in advance and use a drip acclimation method (replace 1/5 of the water per hour).
II. Abnormal Water Quality
- Ammonia/Nitrite Poisoning: Deteriorated water quality causes chronic poisoning, leading to bottom-dwelling and rapid breathing.
Solution: Immediately replace 1/3 of the water, fast the fish for 3 days, add nitrifying bacteria, and test water quality (ammonia should be <0.05mg/L).
- Improper Water Changes: Replacing too much water at once (>2/3) or adding chlorinated tap water directly can cause stress.
Solution: Let tap water sit for 3–5 days before use, and never replace more than 1/3 of the water at a time.
III. Health Issues
- White Spot Disease/Parasitic Infection: White spot disease incidence surges by 300% in low temperatures, with affected fish rubbing against the tank and developing white spots.
Solution: Raise the temperature to 30°C and bathe the fish in methylene blue (2 drops/L); use anti-white spot medication for severe cases.
- Enteritis/Ascites: White feces, loss of appetite, and bottom-dwelling signal potential enteritis.
Solution: Mix metronidazole with feed (1 tablet/kg feed) and feed for 5 consecutive days.
IV. Environmental Adaptation and Stress
- New Fish Acclimation Stress: Transportation fatigue or environmental changes can cause temporary bottom-dwelling.
Solution: Lower the water level to 5cm above the fish, add Indian almond leaves, and fast the fish for 3 days in a quiet environment.
- Sudden Scare or Light Changes: Bright lights or noise can make bettas hide at the tank bottom.
Solution: Minimize disturbances and maintain a stable environment.
V. Additional Considerations
- Substrate Selection: Sharp gravel may scratch the fish’s abdomen. Use 0.3–0.5mm perlite (sterilized with boiling water).
- Winter Feeding Adjustments: Reduce feeding by 30% in low temperatures, prioritizing high-protein feeds (≥40% protein).
If no improvement is seen after adjustments, further inspect the fish for symptoms (e.g., swollen gills, white films on the body) to identify the root cause.