Why Is My Guppy Fat & Bloated? Is It Actually Pregnant?

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While I put a lot of effort into keeping my fish healthy, sometimes I notice things that get me worried. For example, I saw that my guppy fish appeared swollen, with fat and bloated belly. To determine whether it was sick or merely pregnant, I started investigating the issue pretty extensively.

Guppies become fat and bloated usually due to pregnancy, accompanied by a gravid spot and behavioral changes, such as aggression. However, guppies also appear swollen due to Dropsy disease (caused by a bacterial infection), inappropriate water conditions, constipation, and overfeeding.

As we move forward, I will show you how to distinguish a pregnant guppy from a sick one to act accordingly. I will also teach you how to deal with underlying ailment conditions, such as constipation and Dropsy.

Also Read: Guppies Diseases

What Makes Your Guppy Fat & Bloated?

It isn’t normal for guppies to be fat or bloated. And you are right in assuming that your guppy might be pregnant. Guppies are live-bearers. That means that their eggs are fertilized in their bodies, and they eventually give birth to live fry.

But before a guppy gives birth, the creature’s belly will first swell to indicate the presence of fry on the inside. But that only applies to female guppies. They are the only gender that can give birth. What if your fish is male? Better yet, what if your guppies are female, but they have already given birth, and yet their bellies are still bloated? 

Well, bloating in guppies has various causes besides pregnancy, with the most notable including:

1. Constipation and Indigestion

If your guppy isn’t pregnant, you should consider constipation. Like humans, fish can suffer from constipation resulting from overfeeding and indigestion.[1] Bloating resulting from constipation can lead to swim bladder disorder, affecting the guppy’s ability to swim.

You can cause constipation and bloat in general, by feeding your guppy an abundance of dried and protein-rich foods. These might eventually get stuck in the digestion system. A common sign of constipation in fish is long and stringy fecal matter hanging from the back.

Also Read: Guppy Fish Swimming Vertically

2. Weight Gain

Some fish are fat because they overeat. They are neither sick nor constipated. They have merely gained weight. One way of determining whether your guppy is fat and not sick is to look for additional illness signs.

If the guppy is perfectly healthy and you haven’t observed a loss of appetite, lethargy, or fading colors, it isn’t in danger. Yet, trouble could arise down the line if you keep overfeeding the creature. Bear in mind that healthy guppies won’t feel satiated and keep eating as long as you feed them.

3. Dropsy Disease

Dropsy has numerous causes. That includes low water quality, high concentrations of toxins (like ammonia and nitrites), stress, drastic shifts in temperature, and poor nutrition, to mention but a few.[2] A guppy with Dropsy will manifest a swollen belly. 

The condition typically occurs due to a bacterial infection. The bacteria responsible for the disease lives in most aquariums, although immunocompromised fish may develop a severe infection. That will cause the belly to drop down, hence the name.[3]

Therefore, if you’ve noticed that the bloated guppy was relatively sluggish before its belly began to swell, Dropsy could definitely be the reason. But that isn’t enough to prove that it has a Dropsy disease. It would help if you also looked for bulging eyes, pale gills, and protruding scales. Keep in mind that Dropsy might eventually kill most of your guppies.

4. Infection

Bacterial, parasitic, and viral infections can cause bloating by allowing fluids to accumulate in the guppy’s abdominal cavity. That will affect the creature’s organs in the long run. Stressed fish living in unhygienic conditions are more susceptible to infections of this sort.

It is hard to distinguish Dropsy from other infections since the fish will appear sluggish and pale in both cases. It will also show less interest in food and will swim at the upper sections of the tank. Luckily, the treatment for both cases is the same (as you will see later on).

Also Read: Guppy Losing Tail, Scales and Fins

5. Tumors

Some guppies swell because they have tumors and growths. While tumors can develop anywhere in the fish’s body, they could definitely involve the abdomen, in which case the fish will appear fat and bloated. 

Tumors in fish could be secondary to numerous reasons, including viruses such as retroviruses.[4] In the case of a tumor, you will typically see a bulging point, while the rest of the area appears normal. Sometimes, these tumors are benign. However, in some cases, they are not. 

6. Pregnancy

If your guppy has already given birth, but it is still fat, don’t be so quick to assume that pregnancy is no longer the bloating cause. Generally, female guppies have to mate with male guppies before they can give birth. Then, the eggs in a female guppy’s body must be fertilized by a male guppy’s sperm. 

However, the female guppy can store that sperm for several months at a time.[5] That allows the fish to continue giving birth every 28 days, even in the absence of a male guppy. In other words, if your guppy is bloated, it might be pregnant once again.

How to Treat Guppies with a Swollen Belly?

It would be best if you customized your treatments to match the cause of the bloating in your guppies, for instance:

1. Dropsy Treatment

Dropsy is a dangerous condition. It would be best if you attack the illness the moment you notice the signs. That includes moving the guppy to a separate tank that has been cycled sufficiently and whose parameters match the original tank.[6]

I also recommend adding some Epsom salt (1 teaspoon for each gallon). I personally use the Solimo Epsom Salt (link to Amazon). It would help if you also introduced some antibiotics to the tank. My first way of choice would be using the API MELAFIX Fish remedy (link to Amazon)

You can also add antibiotics to the guppy’s food. However, you should know that, in many cases, Dropsy can’t be treated. Most fish that the illness attacks die, so many aquarists prefer to euthanize guppies that show signs of Dropsy.

2. Improving the Tank’s State

Try to improve the conditions in your guppy tank as much as you can. Start by testing for toxins like ammonia. High concentrations of the substance can compromise your guppy’s immune system. One sign of ammonia poisoning in guppies is air gasping.

That is where I would highly recommend the API Aquarium Test Kit (link to Amazon). That is the most cost-effective bundle I could find after numerous tests. It will tell if the ammonia, nitrates, nitrites, and pH are out of the desired range within minutes.

You can combat toxins by performing regular water changes. Start by replacing 30-50% of water weekly. After a while, you can lower it to 10-15%. You can also use products like ‘Amquel’ and ‘Prime’, especially if your guppies are so sick that you don’t want to expose them to the stress that water changes induce.

One way of preventing Dropsy is to perform frequent water changes. That will lower the level of the bacteria that is responsible for the condition. I also recommend avoiding overcrowding. The more fish you have in the tank, the harder it becomes to keep the water clean.

You shouldn’t neglect a filter, either. Water changes are useful, but they must work with a filter to keep your water clean. Then, endeavor to monitor the pH levels. The wrong pH can ruin the balance of your tank. Generally, bloated fish are more likely to recover if the conditions in their tank are favorable.

3. Feed Your Guppies Properly

First, avoid overfeeding your fish. Guppies should only eat twice a day at the most. Try giving them meals in quantities they can consume within the first 40 or so seconds. If you see leftovers within that time range, you should probably feed them less next time.

I also recommend maintaining a balanced diet that includes freeze-dried brine shrimp, blood worms, tubifex worms, spirulina tablets, flakes, and veggie pellets. Besides bloated guppies, keeping a balanced diet also treats pale guppies that have lost their color.

If you suspect that your fish is constipated, stop feeding it for a few days. Once you resume meals, give it cooked, peeled peas. You can also try Daphnia. Some people even use Epsom salt to combat constipation. It relaxes the intestinal muscles.[7]

4. General Infections Treatment

It is possible to overcome infections with water changes and healthy meals, mostly if your guppy lives in a stress-free environment filled with plants and devoid of bullies. However, in many cases, it is necessary to treat it with antibacterial medication.[8]

As mentioned above, I recommend using remedies like the API MELAFIX. It has more chances of curing general infections if Dropsy isn’t the case. However, in general, I recommend consulting vets. They can point you in the direction of effective chemical treatments.

Fat Guppy vs. Pregnant Guppy

These signs indicate that your guppy is pregnant:

  1. The guppy fish will become less active and swim slowly.
  2. Aggression towards approaching fish will occur, including the male guppy.
  3. The pregnant guppy will develop a gravid spot, a triangular stain near the anal vent.
  4. The fish will spend more time hiding behind vegetation and decorations.
  5. Black lines will appear on the belly, which represent the fry’s eyes.

If the signs above are presented in your guppy fish, you may assume that the swollen belly is due to pregnancy and not an ailment. Here is more information about pregnant guppies that you should seek:[9]

  • Gender – Only female guppies can give birth. If your guppy is male, it is merely fat. It can’t be pregnant. Male guppies are more colorful, with big tails and a long, pointed anal fin. The anal fin on a female guppy is triangular.[10]
  • Belly – A pregnant guppy’s belly isn’t merely swollen. It will continue to expand as the pregnancy progresses, with the guppy taking on a large, boxy shape as the fish nears its due date.
  • The Gravid Spot – If you want irrefutable evidence proving that your guppy is pregnant, look for the gravid spot. It is found below the abdomen. The spot becomes darker while also growing in size as the pregnancy advances.[11]
  • Behavior – A pregnant guppy spends a lot of time hiding in the foliage.[12] It will either refuse food or eat much smaller amounts, especially when it nears its due date.

However, if the guppy is bloated due to an underlying disease, you will observe additional symptoms besides a swollen belly. These include a red anus, stringy feces, gasping, protruding scales, and fading colors.


If your swollen guppy is a female, which also presents aggressive behavior and a typical gravid spot, it is probably pregnant. Besides appearing bloated, the fish should look okay without any signs of illness. 

However, if your guppy also looks sluggish or has lost its colors, you should treat a potential disease. Start by quarantining your fish, so it doesn’t infect the rest of its tankmates. Then, water testing and antibiotics should be your next considerations.

If your guppy suffers from Dropsy, water changes, and MELAFIX could solve the issue, although the chances for that are relatively low. At this point, you should minimize collateral damage by putting the sick guppy in a separate tank while looking for similar symptoms in the rest of your fish.


  1. https://guppyexpert.com/guppy-fish-swollen/
  2. https://guppyexpert.com/guppy-fish-dropsy-disease/
  3. https://www.thesprucepets.com/dropsy-in-aquarium-fish-1381806
  4. https://www.msdvetmanual.com/exotic-and-laboratory-animals/aquarium-fishes/neoplasia-of-fish
  5. https://aquariumadviser.com/how-to-tell-if-guppies-are-pregnant/
  6. https://drguppy.com/guppy-fish-dropsy/
  7. https://www.myaquariumclub.com/bloating-4064.html
  8. https://www.cuteness.com/article/treat-bloated-fish
  9. https://www.wikihow.com/Find-Out-if-Your-Guppy-Is-Pregnant
  10. https://guppyaquarium.com/identifying-male-female-guppy-fish
  11. https://small-pets.lovetoknow.com/pregnant-guppy-fish
  12. https://fluffyplanet.com/is-my-fish-pregnant-fat-or-just-bloated/