We are reader supported. When you purchase through links on our site, we may earn an affiliate commission. Also, as an Amazon affiliate, we earn from qualifying purchases.
Dropsy is one of the most worrying problems an aquarist can face. A fish that suddenly looks swollen, with scales sticking out like a pinecone, is hard to ignore. The good news is that if you act fast, you can sometimes save the fish and prevent the same issue from happening again. In this guide, I will explain what dropsy really is, how to spot it early, what steps to take right away, and how to treat it safely. I will also give you a clear, beginner-friendly plan and share prevention tips so your tank stays healthy long-term.
What Is Dropsy?
The term and why it is confusing
Dropsy is not a single disease. It is a syndrome, which means a group of symptoms that happen together. The word “dropsy” describes visible swelling and fluid buildup, not the exact cause. Many different triggers can end in dropsy, which is why it is confusing and why one solution does not fit every case.
When hobbyists say “my fish has dropsy,” they usually mean the fish is bloated and its scales are raised like a pinecone. This pineconing look is very important, because it often signals internal organ failure or severe infection. That is why dropsy is serious and needs quick action.
What actually happens inside the fish
In most cases, dropsy is the result of a bacterial infection that has reached the internal organs. As the kidneys and other organs struggle, the fish cannot regulate fluids and salts well. Water moves into the body cavity and tissues. The fish swells, and the skin stretches so the scales lift outward. This is why you see the classic pinecone appearance.
Fluid buildup can press on the swim bladder and gut, so the fish may float oddly or stop eating. Without rapid treatment, organ failure can progress and the fish may not recover.
Common Causes and Risk Factors
Opportunistic bacterial infection
Most cases are linked to Aeromonas or similar gram-negative bacteria. These bacteria are often present in tanks, but healthy fish fight them off. When a fish is stressed, injured, or living in poor water conditions, bacteria can quickly take advantage and invade internally. Once inside, the infection becomes hard to reach without strong, targeted treatment.
Water quality problems
Ammonia or nitrite above 0 ppm, high nitrate, unstable pH, or large temperature swings weaken the immune system. Bad water does not always kill fish right away, but it sets the stage for infection. Gunk in the substrate, dirty filters, and infrequent water changes all raise the risk. Overcrowding also increases waste and stress.
Stress, diet, and other triggers
Constant bullying, fin-nipping, or chasing uses up a fish’s energy and harms immunity. A poor diet, old or rancid food, sudden diet changes, and overfeeding can cause gut issues that open the door for infection. New fish that were not quarantined can bring bacteria or parasites. Cold stress is another trigger; tropical fish kept too cool or goldfish exposed to quick temperature swings are more likely to get sick.
Species that seem more vulnerable
Any fish can get dropsy, but bettas, fancy goldfish, dwarf gouramis, and balloon-bodied livebearers are seen with it more often. These fish either have special body shapes or are frequently bred in ways that can make them more sensitive to water quality and stress. Knowing your species’ needs gives you a head start in prevention.
How to Identify Dropsy Early
Subtle early warning signs
Look for a fish that is withdrawn, resting low in the tank, or hiding more than usual. Watch for loss of appetite, spitting out food, or stringy white poop. Clamped fins, slightly raised scales that are not obvious yet, dull color, or a faintly swollen belly are early clues. Catching these signs can change the outcome because you can start supportive care before full-blown pineconing appears.
Classic signs of dropsy
As fluid builds, the belly swells, the body looks puffy, and scales lift so the fish looks like a pinecone when viewed from above. Eyes may protrude, and the fish often breathes faster. It may float awkwardly, have trouble staying level, or rest on the bottom. When pineconing is obvious, the condition is advanced and the prognosis is guarded. You still should treat, but understand it may be hard to reverse.
How to tell dropsy from similar problems
Constipation usually causes swelling but not pineconing; the fish may still be active and will often pass stool after fasting or eating a skinned pea. Egg-binding in females causes swelling on one side or a firm, egg-shaped look, without raised scales. Swim bladder disorder changes buoyancy but does not cause fluid buildup or pineconing. Internal parasites can cause stringy white feces and wasting rather than big swelling. If scales are raised and the body is uniformly puffy, think dropsy.
Immediate Actions When You Suspect Dropsy
Move the fish to a hospital tank
Set up a small hospital tank or container with gentle filtration and strong aeration. A bare-bottom setup makes it easy to keep clean. Use water from the main aquarium to match parameters, and keep the temperature stable. Remove carbon from the filter before using medications because carbon absorbs meds. A simple sponge filter and an air stone are ideal. Isolation prevents stress from tankmates and lets you medicate without affecting plants or invertebrates.
Test water and correct basics
Test ammonia, nitrite, nitrate, pH, and temperature. Ammonia and nitrite must be 0 ppm. Keep nitrate as low as possible, ideally under 20 to 40 ppm. Match the temperature to the species: most tropical fish prefer 25 to 27°C (77 to 81°F). Goldfish do best cooler, around 20 to 23°C (68 to 73°F), with minimal swings. Do a partial water change if needed to correct poor water. Stable, clean water is the foundation of recovery.
Withhold food for the first 24 hours
A brief fast reduces metabolic load and waste. Many sick fish are not interested in food anyway. After 24 hours, you can offer small, high-quality foods. Avoid overfeeding at all costs, and remove uneaten food immediately.
Treatment Options
Epsom salt for fluid relief
Epsom salt (magnesium sulfate) can help draw fluid out of the body by osmosis. Use only plain, unscented Epsom salt. There are two approaches:
Short bath: Prepare a separate container with tank water and add about 1 tablespoon per gallon (roughly 15 grams per liter). Match the temperature and aerate the bath. Place the fish in for 10 to 15 minutes while you watch closely. If the fish shows distress, stop the bath early. This can be repeated once daily.
Gentle in-tank dosing: For the hospital tank, use about 1 teaspoon per 5 gallons (about 0.5 grams per liter) to start. This lower level is safer for continuous exposure. Do not use both high-dose baths and heavy in-tank dosing at the same time. Re-dose after water changes as needed. Avoid Epsom in planted display tanks and with sensitive species unless isolated.
Note that Epsom salt is different from aquarium salt. Aquarium salt (sodium chloride) can support gill function and reduce nitrite toxicity, but it does not pull fluid from tissues like Epsom does.
Antibiotics for internal infection
Because dropsy is often bacterial, antibiotics that target gram-negative bacteria are the main treatment. Options can include kanamycin, nitrofurazone, oxytetracycline, or minocycline, depending on what is available where you live. Many aquarists use a combination such as kanamycin with nitrofurazone because they can work well together. Follow the product label for exact dosing and re-dosing schedules, and maintain strong aeration because some medications reduce oxygen.
If your fish is still eating, medicated food is excellent because it delivers the drug inside the gut, closer to the infection. Some aquarists bind antibiotics to food using a commercial binder so the medication stays in the pellet. Offer small portions twice a day for 7 to 10 days. If the fish is not eating, use water-dosed medications as directed.
Regulations vary by country. In some places, certain antibiotics require a veterinarian. If you cannot access antibiotics, focus on clean water, Epsom support, and mild antibacterial products made for aquariums, understanding that success rates are lower in advanced cases.
What to do if strong antibiotics are not available
Some regions have over-the-counter antibacterial remedies aimed at external infections. These may help only in very mild or early cases. Products like broad-spectrum antiseptics can reduce bacterial load, but they rarely cure advanced internal infections. Indian almond leaves (catappa) add gentle tannins that may soothe and mildly inhibit pathogens. Clean water, low stress, and Epsom support remain essential. Be realistic: if pineconing is severe, the outcome is uncertain without proper antibiotics.
Supportive care that improves survival
Keep the hospital tank dim and quiet. Increase aeration because sick fish need more oxygen, and medications reduce oxygen levels. Keep temperature stable and appropriate for the species. For tropical fish, a slight increase within their safe range can support the immune system, but avoid big jumps and avoid overheating. For goldfish, do not chase high tropical temperatures; stable and moderate is better. Add a hiding place like a piece of PVC or a small cave to reduce stress. Do daily small water changes to maintain water quality, replacing medication as directed.
Feeding during treatment
Once the fish shows interest in food, offer easily digestible foods such as daphnia or bloodworms in small amounts. Avoid high-air, very dry pellets at first. The popular “pea cure” only helps with constipation, not bacterial dropsy, so do not rely on peas if pineconing is present. If using medicated food, feed tiny, frequent portions to avoid waste. Remove leftovers immediately.
How long until you see improvement
In a best-case scenario, you may see reduced swelling, better appetite, and more natural behavior in 3 to 5 days. Pineconing can take longer to subside, and sometimes the scales never lie perfectly flat again even if the fish stabilizes. If the fish worsens or shows no change after a full, correctly dosed course, the prognosis is poor.
Step-by-Step Plan for Beginners
Day 0: Isolate and stabilize
Move the fish to a hospital tank with clean, matched water. Add gentle aeration, remove carbon, and dim the lights. Test ammonia and nitrite; both must be 0 ppm. Do a 25 to 50 percent water change if needed. Withhold food for 24 hours. Give an Epsom salt bath for 10 to 15 minutes if the fish is strong enough, then return it to the hospital tank. Do not use high-dose bath if the fish is very weak; choose gentle in-tank Epsom dosing instead.
Day 1 to 3: Start medication and monitor
Begin a gram-negative antibiotic per the package. Increase aeration. Keep temperature stable. If the fish begins to eat, start medicated food as directed and reduce water-dosed meds if the label tells you to. Watch for signs of improvement: slightly less swelling, more interest in food, calmer breathing. Do small daily water changes of 10 to 20 percent, replacing any removed medication according to the label.
Day 4 to 7: Continue the course
Maintain the antibiotic schedule without skipping doses. Repeat Epsom baths once daily if the fish tolerates them, or keep the gentle in-tank Epsom level steady. Keep stress low; avoid sudden light changes or tapping the glass. Offer tiny meals once or twice a day. Clean the bottom of the hospital tank daily to remove waste.
Day 8 to 14: Reassess and finish treatment
If the fish is improving, finish the full medication course. Do not stop early even if the fish looks better. If there is no improvement, consider a different antibiotic that targets gram-negative bacteria, or seek veterinary advice if possible. Continue pristine water quality and stable conditions. Only after the fish is stable for a full week should you consider returning it to the main tank.
When to Seek Help or Consider Humane Euthanasia
Signs of severe organ failure
If the fish is unable to stay upright, not eating for several days, showing extreme pineconing, bleeding sores, or lying listlessly despite treatment, it may be suffering. Advanced dropsy often has a poor prognosis. Continuing aggressive treatment may prolong stress without real benefit.
Getting expert help
If you have access to an aquatic veterinarian, they can prescribe the most effective medications and advise on dosing for your specific fish and water. They can also help rule out parasites or other causes.
Humane euthanasia
If recovery is unlikely and the fish is suffering, humane euthanasia may be the kindest option. Many aquarists use clove oil in a separate container to gently anesthetize the fish before increasing the dose. Do not freeze or flush a live fish. Check local guidelines or consult a veterinarian for the most humane method.
Prevention: Keep Dropsy from Returning
Quarantine new arrivals
Quarantine new fish for 3 to 4 weeks in a separate tank. Watch for signs of illness and treat if needed before introducing them to your display tank. Rinse live plants and consider a short quarantine period for plants to avoid hitchhiking pests. Quarantine reduces the chances of bringing in new pathogens.
Stay on top of water quality
Do regular water changes, usually 25 to 40 percent weekly, depending on stocking and feeding. Vacuum the substrate, rinse filter media gently in tank water, and avoid over-cleaning that kills beneficial bacteria. Keep ammonia and nitrite at 0 ppm and nitrates low. Test weekly until you know your tank’s rhythm, then at least monthly. Stable pH and temperature matter more than chasing a perfect number.
Feed smart, not more
Offer small, varied meals. Use high-quality pellets or flakes and supplement with frozen or live foods. Avoid feeding more than the fish will eat in a couple of minutes. Soak very dry pellets briefly if your fish tends to gulp air. Store food in cool, dry places and replace old containers regularly. Overfeeding is a common cause of gut stress and poor water quality.
Stock and match correctly
Do not overcrowd. Choose tankmates that share similar temperature and water needs and that will not bully each other. Keep schooling fish in proper group sizes. Provide hiding spaces and visual barriers to reduce stress. A calm, well-matched community is far less likely to suffer disease outbreaks.
Keep temperatures stable
Use a reliable heater with a thermostat for tropical tanks and consider a chiller or fans in hot climates. Sudden swings stress fish. Aim for slow, gentle changes when adjusting temperature. For goldfish, avoid rapid fluctuations and keep the tank out of direct sunlight or drafts.
Frequently Asked Questions
Is dropsy contagious?
The outward symptom of dropsy is not contagious by itself, but the bacteria involved can be present in the tank and can infect other stressed fish. That is why quarantine, clean water, and reducing stress are important for the whole aquarium.
Can a fish recover from dropsy?
Yes, if caught early and treated properly, some fish recover and live normal lives. When pineconing is severe and the fish is very weak, the chance of recovery is lower. Acting quickly makes the biggest difference.
Should I treat in the main tank?
It is better to treat in a hospital tank. Medications can harm plants, invertebrates, and the biological filter. Hospital tanks also allow more precise dosing and gentler conditions. Only treat the display tank if absolutely necessary and if it has no sensitive inhabitants.
Which salt do I use?
Use Epsom salt (magnesium sulfate) to help pull fluid from tissues. Aquarium salt (sodium chloride) is different and does not have the same effect on swelling. Always dose carefully and avoid using salt in planted or invert-heavy display tanks.
How much Epsom salt is safe?
For short baths, about 1 tablespoon per gallon for 10 to 15 minutes while closely observing the fish. For in-tank support in a hospital tank, about 1 teaspoon per 5 gallons is a gentle starting point. Re-dose after water changes and avoid prolonged high concentrations.
Will peas fix dropsy?
Peas can help with simple constipation, but they do not cure bacterial dropsy. If you see pineconing, focus on antibiotics, Epsom support, and perfect water conditions.
Can plants and shrimp handle medication?
Many antibiotics and salts are not safe for plants, snails, or shrimp. Treat the sick fish in a separate hospital tank to protect your display tank’s ecosystem.
Extra Tips for Better Outcomes
Look from above daily
Make it a habit to gently look down at your fish from above. Slight lifting of scales is easier to see from this angle and helps you catch trouble early when treatment is most effective.
Keep a basic fish first-aid kit
Have Epsom salt, a spare air pump and sponge filter, a small heater, test kits for ammonia, nitrite, nitrate, and pH, and a broad-spectrum gram-negative antibiotic that is legal in your region. Keep everything together so you can react quickly.
Record what you do
Write down water test results, doses, and your fish’s behavior each day. Notes help you spot patterns, avoid missed doses, and learn what works best in your setup.
Conclusion
Key takeaways you can put into action
Dropsy is a serious syndrome caused by internal fluid buildup, usually from a bacterial infection made worse by stress and poor water conditions. Early detection is critical: watch for appetite changes, subtle swelling, clamped fins, and especially pineconing. Act quickly by isolating the fish, stabilizing water, using Epsom salt for fluid relief, and starting an appropriate antibiotic if available. Supportive care with oxygen, warmth within the species’ safe range, low stress, and careful feeding improves survival.
Long term, prevention matters most. Quarantine new fish, maintain clean and stable water, feed modestly with quality foods, and stock your tank sensibly. With these habits, you will see fewer illnesses and enjoy a vibrant, healthy aquarium. If a case becomes advanced, be compassionate and realistic, seek help if you can, and always prioritize the fish’s welfare. Consistent, calm care is the aquarist’s best medicine.