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Bloodfin Tetra Wasting and Balance Issue

Matt Armstrong

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Long story short: I have a tetra that has two symptoms that started out subtle and have become slowly but progressively worse over a span of two months. I'd like advice as to how to proceed. Primarily:

  1. Should I treat with salt or meds? Which ones?
  2. Should I treat the whole tank or just the one fish?

I included a video at the end showing this fish's balance issue (in a tank with the filters off).


  • This tetra started off thinner than the other two, and has become concave near its pelvic fins.
  • This tetra has a balance issue. Its tail end "sinks" when it rests. It must work much harder than its species-mates to maintain its position in the tank.
  • This tetra otherwise behaves "normally". It eats as eagerly as the others, shoals with them, etc.

Tank parameters are:

  • pH: 7.6 to 7.8 (stable, same as my tap)
  • Nitrates: As high as 40-80 (I can't tell the difference between 40 and 80 with the API test kit) but I've reduced this to <20ppm with water changes recently. I've stopped dosing ACO "Easy Green" for now, but initially I dosed enough to raise this to 40ppm as recommended. Also, I suspect the "half decomposing" Amazon Sword was a larger source of Nitrates than I realized at the start -- I now prune and remove all decomposing leaves weekly.
  • 3-5 dGH
  • 3 dKH
  • 0 Nitrites
  • 0 Ammonia
  • 76F

A few weeks ago, trying to help this fish, I put this tank through the ACO Quarantine procedure at https://www.aquariumcoop.com/blogs/aquarium/how-to-treat-sick-aquarium-fish. No change in this one fish's symptoms. This did impact the Nitrogen cycle in the tank, and I went through a few days where some fish showed stress, and Ammonia and Nitrites were non-zero. I gave them some relief by dosing Prime daily until the cycle re-established itself in about three days.

This is a 20 gallon tank, which I took on from another person at the end of November. It came with 3 Bloodfin Tetras (Aphyocharax anisitsi), three "Kerri Tetra" (aka Blue/Purple Emperor Tetra Inpaichthys kerri), and a Bristlenose. It also had zero filtration, one sad and half decomposing Amazon sword failing to root in 1/2" of gravel, a rarely used and very dim old fluorescent canopy, and a heater set at 78F.

I've since added the smallest Eheim canister filter (which I already had), a sponge filter, a descent light, and four more Inpaichthys kerri, which evened out their intera-species aggression (before these, I'd never seen one tetra bully another so much that it went and hid in a corner!).

From the start, one of the Bloodfin Tetras looked stunted, with a smaller than usual head, and "shiny" eye sockets when viewed from the front and top (compared to the other two, this stunted fish has less flesh around its eyes). This fish appears otherwise healthy. See if you can spot it in the video, but I'm not worried about this fish.

Another of the Bloodfin Tetras is the subject here. This one was thin when I got it, which I initially thought suggested it was a male. I then noticed that its tail "sank" more than the others -- it must constantly work to stay horizontal. This has progressed, slowly, to become ever so slightly worse over two months. This fish has also gone from thin to skinny to concave. Other than this, behaviorally, it acts normally, eats, etc.

The third Bloodfin is fat and appears happy.

The behavior is hard to capture in pictures, but is pretty clear in a video. The fish I'm worried about is the one whose caudal (tail) fin is lower than the rest of its body. The filters and air were off for this filming.


Edited by Matt Armstrong
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High levels of nitrates can effect fish's  swim bladder if it was getting to 80ppm for a long period of time this could have damage your fish's swim bladder some  internal types of internal parasites can also effect fish's swim bladders  and cause sunken belly that can be a sign of wasting disease I think it would be worthwhile treating for parasites @Odd Duckhas a good treatment schedule I think it would be worthwhile to follow this treatment plan IMG_20230127_231638.jpg.6b7a1415eacb0ca821e51e2f6219d7d4.jpg

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  • 3 weeks later...

An update on this treatment regime:

I moved all fish from this tank to a bare bottom 10G quarantine tank and began treating as described above. So far, I observe no change in any of the fish, for better or worse. The one Bloodfin tetra still has a compromised swim bladder but it hasn't gotten worse or better.

One interesting behavioral thing I have noticed. The Bloodfin tetras (Aphyocharax anisitsi) appear to happily feed at all levels of the tank. They are primary top and mid-water feeders, but they will also orient themselves vertically and peck at the substrate. That is, except for this one tetra with the swim bladder issue. It is "tail heavy" and doesn't seem able to do this, and it also doesn't seem to feed quite as effectively since it must constantly correct the tendency for its tail to drop. These tetras are also "thrown off" by the bare bottom tank and even after weeks still seem to swim against the bare bottom in the belief they can still swim deeper.

In contrast, the Inpaichthys kerri tetras (Blue/Purple Emperor Tetra) almost completely ignore the tank bottom, rarely feed off it, and routinely beat the Bloodfin tetras to food at the upper levels.

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