Neon Tetra Mystery Bloating?


Hey all,

I have a 55 gallon freshwater tank very understocked:
- 21 neon tetra
- 3 lemon barb (passive)
- 1 blue gourami
- 1 clown pleco

0/0/.02 for test readings
7.1 ph

I do a 33% wc every month or so, and I have very good filtration.

Recently, one of my Neon Tetras developed what I assumed to be swim bladder. Bloating of stomach, inability to swim correctly, tilting, unable to eat. I put him in a breeder box for isolation. Three hours later, he was belly up. What I noticed is that his stomach had bloated completely, to the point where it had almost come out of his body. I also observed small black dots, what looked to be bugs, on the belly. I have attached a video post-mortem for those who care to observe: (warning, not the prettiest)

What I am looking to know is... was this swim bladder? Is anyone familiar with these "bug" things that can be seen? I am worried that there is an invasive and deadly disease or species in the tank that I should take action on. Please get back to me if you can offer help!


How long had the fish been dead? It looks like gnats or fruitflies got to the body. If that's not the case I have no idea what type of parasite those could be. That looks pretty wild and I've never seen anything like it.
Bloating is typically caused from either a bacterial problem or an intestinal blockage. Typically if you have a healthy tank and haven't added any fish in a while the fish is just having belly problems and the issue will resolve. Usually those are the more minor cases that pass with fasting and the fish doesn't usually die, so it concerns me that it passed away. It cod be a sign it's a bacterial problem


Actually that's not that under stocked, your maybe have under 10" of space for more fish. That's not enough water changes for that aquarium. You should try and change at least 25% every week, and maybe get a quarantine tank for the tetra if possible.

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