Neon tetras are one of the more common entry level fish due to how easy they are to care for, their low price tag, and how well they do in a small, single species tank.
Although they are a very low maintenance fish, we have noticed a number of people having problems with their neon tetra having a big belly recently.
Try to and help as many of our readers as possible, we have decided to publish this article going over the 7 most common reasons that your neon tetra has a big belly.
This list will cover the most common reasons that your neon tetra may swell or bloat up, especially around the belly area to try and help you narrow down the potential problems.
Please note that without seeing photographs of your neon tetra, it is difficult to diagnose exactly what is wrong with your fish.
An experienced fish keeper in your local area may be able to help with this though as they can come and check your fish but if that’s not an option, our list below should still help.
Your Neon Tetra Is Pregnant!
The most common reason that your neon tetra will have a big belly is due to the fish being “pregnant”.
Now, neon tetras are not live bearers so they don’t technically get pregnancy but the build up of eggs in the female neon tetras prior to spawning can cause the fish to have a big belly.
Due to the reasons behind the big belly in the neon tetras, the swelling tends not to occur anywhere else on the fish. After a week or so, the eggs will usually be released and the fish will return to its normal size.
Other symptoms of a pregnant neon tetra include the neon tetra becoming noticeably more rounded than usual and the female neon tetras may also have a slight change in coloration.
The Neon Tetra Has Internal Worms!
Internal parasites can be another reason that your neon tetras belly may look big due to the additional space that the internal worms are taking up.
These parasites can cause a neon tetra to bloat up and look like they are pregnant when they are not.
As well as looking like they are pregnant, neon tetras with internal parasites may also have a change in behavior. The neon tetra may become more lethargic than usual and may stop eating as much.
Thankfully, there are a number of treatments such as Melafix and Pimafix that you are able to use that should be able to treat most types of internal parasites. Some types of internal worms may require a specialist treatment though.
You Have Been Overfeeding Your Neon Tetra So Its Fat!
Overfeeding is very common for people new to the fish keeping hobby and this can make your neon tetra fat and give it a big belly.
It is important to only feed your neon tetra what it can eat in 2 minutes and then remove any uneaten food as it can quickly start to pollute the water if left in the tank.
A neon tetra that has been overfed will have a very noticeable swelling around its belly area and may also have trouble swimming.
This is due to the extra weight that the neon tetra is carrying and the neon tetra may also have a change in behavior, becoming more sluggish than usual.
You can help your neon tetra lose weight by doing regular water changes and feeding it a smaller amount each day. You should also remove any uneaten food from the tank as soon as possible to prevent your neon tetra from eating it later.
Due to how much neon tetras swim each day, it should be able to drop the additional weight quickly.
The Neon Tetra Has Constipation!
So many people accidentally feed their pet neon tetras an unsuitable fish food product that causes the fish to end up with constipation.
Not only can this make the neon tetra have a big belly but it can also cause a number of other digestive issues as well as cause the poop of the neon tetra to be stringy.
Switching over to a suitable neon tetra fish food can be enough to prevent future constipation problems in the fish. Just keep in mind that your neon tetra will have to pass the food currently in its system before the new food will take effect.
Other symptoms of constipation in a neon tetra include the neon tetra being bloated, the neon tetra swimming erratically and the neon tetra may even stop eating altogether.
If you believe that your neon tetra has constipation then you can try feeding it a small amount of live food such as brine shrimp or daphnia due to the higher fiber content often being able to help.
Your Neon Tetra Has Dropsy!
Dropsy is a very serious condition that can affect neon tetras and can cause the neon tetra’s belly to look very big. Dropsy is caused by a build-up of fluid in the fish’s body and often results in the death of the fish within days.
In addition to the neon tetra having a big belly, it will also commonly have problems with bloating all around its body.
Our article on treating a bloated neon tetra may be helpful in this situation but if your neon tetra is swelling up due to dropsy, it is likely that the fish will end up dead over the coming days.
Swim Bladder Disease Is Affecting Your Neon Tetra!
Swim bladder disease is a relatively common problem in neon tetras and can cause the neon tetra to have a big belly.
The swim bladder is a small organ located in the fish’s abdomen that helps the fish control its balance and buoyancy. When this organ becomes inflamed, it can cause the neon tetra to have trouble swimming and a swollen belly.
Thankfully, swim bladder disease in neon tetras does tend to be much easier to treat than some other common diseases in the fish. There are a number of suitable treatments on the market that your local fish store should stock as standard but you can also get them online too.