Scales that stick out like a pine cone are the sign. Move the betta to a separate container with clean, warm water today. Caught early, before the scales lift, some bettas recover. Once the pine-cone shape is clear, most do not, and the kind decision may be humane euthanasia.
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The numbers
| Dropsy | Constipation or bloat | Egg-bound female | |
|---|---|---|---|
| Body shape | Swollen all round, often evenly | Belly swollen, mostly below and behind the fins | Belly swollen, white egg spot visible underneath |
| Scales from above | Stick out like a pine cone | Lie flat | Lie flat |
| Other signs | Bulging eyes, pale gills, curved spine, no appetite | Floats or sinks, little waste, still eats | Active, still eats |
| Outlook | Poor once scales lift | Good, usually fixed by a fast | Good, usually passes by itself |
Dropsy is not a disease in its own right. It is fluid building up inside the fish because its organs, usually the kidneys, have stopped working properly. The cause is most often a bacterial infection in a betta already weakened by poor water, cold or age. The sign that gives it away is the scales: seen from above, they stick out from the body like an opened pine cone.
Move the betta to a separate container with clean, warm water today. Caught early, some bettas recover. Once the pine-cone shape is clear, most do not, and it is worth knowing that before you start.
Is it dropsy, or just a swollen belly?
Many things make a betta look swollen, and most of them are not serious. The table above compares them. The test that settles it is the scales.
Look down at the fish from directly above. In a healthy, constipated or egg-filled betta, the scales lie flat against the body. In dropsy they lift away from it, so the outline looks rough and spiky, like a pine cone. That is the fluid underneath pushing them out.
Other signs that point to dropsy:
- Bulging eyes, from fluid building up behind them.
- Pale gills.
- A curved spine, in later stages.
- No interest in food, and very little movement.
If the scales are flat and the betta is still eating, it is more likely constipation or swim bladder trouble, which a few days of fasting usually fixes.
What causes it
Bacteria that live in almost every aquarium can infect a fish whose defences are down. When the infection reaches the kidneys, they can no longer control the water balance, and fluid builds up in the body.
The infection takes hold when something has already weakened the fish:
- Poor water. Ammonia or nitrite above zero, or months without water changes.
- Cold water. Bettas kept below about 76°F, often in unheated bowls.
- Stress. A recent move, an aggressive tankmate, constant disturbance.
- Age. Bettas commonly live three to five years, and dropsy is common in old fish.
What to do today
- Move the betta to a separate container: a small tank or a large clean bucket, with dechlorinated water matched to the main tank's temperature.
- Keep it at 78–80°F with a small heater. Warmth supports the immune system.
- Add Epsom salt at about one tablespoon per five gallons, dissolved before the fish goes in. It can help draw out some of the fluid.
- Change most of the water in the container every day or two, re-dosing the Epsom salt for the new water only.
- Test the main tank's ammonia, nitrite and nitrate, and fix whatever is wrong there.
- Offer a small amount of food daily, and remove anything uneaten after a few minutes.
Antibiotics. Because the underlying cause is usually bacterial, an antibiotic is the main treatment, and it works best in the early stage. Since 2023, US rules have moved many animal antibiotics to prescription-only, and some fish antibiotics are now hard to buy over the counter. A vet who sees fish, or a good local fish shop, can advise on what is available where you live.
Do not add medication to the main tank
Treat the sick fish in its own container. Antibiotics in the main tank damage the filter bacteria, and the other fish do not need them. The main tank needs clean water, not medicine.
Is it contagious?
Dropsy itself does not spread. It is what organ failure looks like in one fish. But the bacteria that usually cause it are in most tanks, and they attack fish that are weakened. If the water quality caused one case, the other fish are in the same water.
Isolate the sick betta, test the main tank, and do a water change if anything reads high. Watch the other fish for the same signs over the next two weeks.
When it is too late
Once the pine-cone shape is clear, the internal damage is usually beyond repair, and most bettas die within days to a couple of weeks. A betta that can no longer swim, eat or stay upright is suffering.
At that point, humane euthanasia is the kind choice. The method most widely recommended for small fish is an overdose of clove oil, which sedates the fish before it stops breathing. A vet or an experienced local fish shop can explain it or do it for you. Never flush a fish or put it in the freezer alive.
What you need
| Item | Why |
|---|---|
| Epsom salt, unscented | For the separate container, at about one tablespoon per five gallons |
| Small adjustable heater | Keeps the separate container at 78–80°F |
| Liquid test kit | To find out whether the main tank's water started it |
Use plain, unscented Epsom salt only. Bath salts with fragrance or oils are toxic to fish.
The one thing worth taking from this
Check from above. Flat scales mean you probably have time and a good chance. Lifted scales mean dropsy, and the earlier you isolate and treat, the better the odds. In both cases, test the main tank, because the water is often where it started.
Questions people ask
Mentioned in this guide
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