A swollen belly in betta fish can stem from various causes, including physiological factors (such as pregnancy or obesity) and pathological factors (such as dropsy, indigestion, parasitic infections, or tumors). Below is a detailed analysis and corresponding handling advice:
1. Physiological Causes
Pregnancy (Female Bettas)
Symptoms
The female’s abdomen is significantly distended, and the area near the anus may appear pink.
Behavior becomes quieter, and she tends to hide in secluded spots.
Handling Measures
Confirm Pregnancy: Observe if the female shows pre-spawning signs, such as nest-building behavior (males blow bubbles to build nests).
Prepare a Spawning Environment: Provide a quiet, hidden spawning area with aquatic plants or driftwood.
Post-Spawning Care: Promptly remove the female to prevent attacks from the male. Meanwhile, pay close attention to water quality management to avoid egg mold.
Obesity
Symptoms
The abdomen is evenly distended, the fish’s body becomes overall plump, and it appears clumsy when swimming.
Causes
Overfeeding, high-nutrient feed, or lack of exercise.
Handling Measures
Control Feeding Amount: Feed 1-2 times a day, and ensure the food is consumed within 5 minutes each time.
Adjust Feed: Choose high-protein, low-fat feed, and avoid feeding high-fat foods like mealworms.
Increase Exercise: Encourage the betta to swim by increasing water flow or placing obstacles in the tank.
2. Pathological Causes
Dropsy (Trichomoniasis)
Symptoms
The abdomen swells rapidly, which may be accompanied by red and swollen anus, stringy feces, or white feces.
The fish loses weight and swims weakly.
Causes
Poor water quality, bacterial infections, or parasitic infections (e.g., Dactylogyrus).
Handling Measures
Isolate the Sick Fish: Move the infected betta to a separate treatment tank to prevent spreading to other fish.
Improve Water Quality: Change water regularly to keep it clean, and use a water conditioner.
Medication Treatment:
Early-Stage Dropsy: Try soaking the fish in a 0.5% salt solution once a day for 10 minutes each time.
Severe Dropsy: Use antibiotics (e.g., yellow powder) or anti-parasitic drugs (e.g., mebendazole) and administer them by feeding or bathing according to the instructions.
Auxiliary Treatment: Maintain the water temperature at around 28°C and increase dissolved oxygen.
Indigestion
Symptoms
The abdomen is distended, which may be accompanied by loss of appetite, floating at the water surface, or sinking to the bottom of the tank.
Causes
Overfeeding, hard-to-digest feed, or sudden feed changes.
Handling Measures
Stop Feeding for 1-2 Days: Allow the betta to digest the food in its body.
Feed Digestible Food: Such as cooked egg yolks or frozen-dried bloodworms (which need to be soaked until soft).
Add Probiotics: Mix a small amount of probiotics into the feed to aid digestion.
Parasitic Infections
Symptoms
The abdomen is distended, which may be accompanied by white spots on the body, red and swollen gills, or abnormal swimming.
Common Parasites
Dactylogyrus, Ichthyophthirius multifiliis (Ich).
Handling Measures
For Dactylogyrus: Use mebendazole or formalin for bathing according to the instructions.
For Ich: Raise the water temperature to 30°C and maintain it, while using Ich medication for bathing.
Isolation Treatment: Move the infected betta to a separate treatment tank to avoid spreading to other fish.
Tumors
Symptoms
Localized swelling in the abdomen, which feels hard to the touch. It may be accompanied by weight loss and difficulty swimming.
Causes
Genetics, environmental pollution, or long-term chronic inflammation.
Handling Measures
Tumors are usually difficult to cure. If they affect the betta’s quality of life, euthanasia may be considered.
Preventive Measures: Keep the water clean and avoid using harmful chemicals.
3. Preventive Measures
Regular Water Changes: Change 1/3 to 1/2 of the water weekly to keep it clean.
Proper Feeding: Feed 1-2 times a day, and ensure the food is consumed within 5 minutes each time to avoid overfeeding.
Observe Behavior: Regularly check the betta’s swimming, feeding, and body color changes to detect abnormalities in a timely manner.
Isolate New Fish: Newly purchased bettas should be isolated and observed for 1-2 weeks. Only put them into the main tank after confirming they are healthy.
Avoid Over-Decoration: Excessive decorations in the tank may scratch the betta or accumulate dirt, polluting the water quality.