Why Is My Betta Fish Bloated? Dropsy, Constipation and Swim Bladder

A swollen belly on an otherwise active betta is one of the most frequently asked questions in fishkeeping forums, and the answer ranges from easily fixable to critically serious. Understanding whether betta fish bloated dropsy constipation or swim bladder disorder is responsible determines whether you need a fasting day or emergency intervention. This guide from Gensou Aquascaping at 5 Everton Park, Singapore, draws on over 20 years of hands-on experience diagnosing and treating bloated bettas for local hobbyists.

Constipation: The Most Common Cause

Overfeeding is behind the majority of bloated betta cases. Betta splendens have short digestive tracts designed for small, frequent insect meals — not the large pellet portions many keepers provide. When food backs up, the abdomen visibly distends, sometimes accompanied by a trailing, stringy faecal strand or no faeces at all.

Treatment is straightforward. Fast the fish for 48 hours — no food at all. On day three, offer a tiny piece of blanched, de-shelled pea or a few frozen daphnia, both of which act as mild laxatives. Bloating from constipation typically resolves within one to two days of fasting. Prevent recurrence by feeding two to three pellets twice daily with one fasting day per week.

Swim Bladder Disorder

The swim bladder is a gas-filled organ that controls buoyancy. When it malfunctions, a betta may float uncontrollably at the surface, sink to the bottom, or swim at a tilted angle. Bloating often accompanies swim bladder issues because the same overfeeding that causes constipation can physically compress the swim bladder.

Fasting and the pea method work when the root cause is digestive pressure. If the fish remains buoyancy-impaired after 72 hours of fasting, a bacterial infection of the swim bladder may be responsible. In that case, treat with a broad-spectrum antibacterial medication and maintain pristine water conditions. Lower the water level to reduce the distance the fish needs to travel to reach the surface for air.

Dropsy: The Serious Diagnosis

Dropsy describes fluid accumulation in the body cavity, causing the abdomen to swell severely and scales to protrude outward — the hallmark “pinecone” appearance when viewed from above. By the time pineconing is visible, internal organs — typically the kidneys — have already sustained significant damage. Dropsy is not a disease itself but a symptom of systemic organ failure, often triggered by chronic bacterial infection or prolonged poor water quality.

Prognosis at the pinecone stage is poor. Epsom salt baths (1 tablespoon per 20 litres of tank water) can reduce fluid retention temporarily. Antibacterial food containing kanamycin gives the best chance if the fish still has appetite. Many experienced keepers, ourselves included, consider humane euthanasia when a fish reaches advanced dropsy with no response to treatment after 5–7 days.

Egg Binding in Females

Female bettas can become visibly swollen with unreleased eggs — a condition called egg binding. The belly appears rounded but smooth, without the pineconing seen in dropsy. The fish usually remains active and interested in food. Egg binding is common in conditioned females that have not been exposed to a male for spawning.

Slight temperature increase to 28 °C, high-protein live food, and patience usually allow the eggs to be reabsorbed naturally over one to two weeks. This is rarely dangerous unless complicated by secondary infection.

Tumours and Internal Growths

Less commonly, bloating results from internal tumours or cysts. These present as asymmetric swelling — one side larger than the other — and progress slowly over weeks or months. Tumours are more frequent in heavily inbred lines and older fish past three years. Unfortunately, there is no effective home treatment for internal growths in bettas. Keep the fish comfortable with clean water and appropriate feeding for as long as quality of life permits.

How to Tell the Difference

Constipation: symmetric belly swelling, no scale protrusion, fish still active, resolves with fasting. Swim bladder: buoyancy problems alongside or instead of visible swelling. Dropsy: severe swelling with pineconed scales, lethargy, loss of appetite. Egg binding: females only, smooth rounded belly, active behaviour. Tumour: slow-developing, often asymmetric, no scale protrusion.

Test water parameters immediately whenever a betta fish bloated concern arises. Ammonia and nitrite should be zero; nitrates below 20 ppm. Poor water quality is the underlying trigger for both constipation (stress reduces gut motility) and dropsy (chronic bacterial infection). A properly cycled tank with consistent maintenance prevents most cases before they start.

Related Reading

• Betta Fish Diseases and Symptoms: Complete Identification Guide
• Betta Fish Feeding Guide: How Much, How Often and Best Food
• Why Is My Betta Fish Turning White? Causes and Treatment
• Betta Fish Water Temperature Guide: Ideal Range and Heater Tips
• Betta Fish Lifespan: Average Age and How to Help Them Live Longer