I have an aquarium with eight Norman's lampeyes (unfortunately 5 male, 3 female) and some other fish. Last Sunday I discovered that one of the Norman's lampeyes wasn't doing so well. She was nearly moving and floated near the surface of the water, head slightly down and tail slightly up touching the surface.

All other fish where fine.

Observed symptom:

  • Hanging near the surface of the water;
  • Fast breathing, but not gasping for air;
  • Not eating;
  • Not using her tail fin;
  • Swims head down tail up.

Other observations:

  • Does not roll to the left or right while swimming (not swimming slanted);
  • Still responsive: reacts on fishnet and tries to escape, which goes pretty well.

Water quality and environment:

All water parameters are fine and did not change in the last weeks. The day before I discovered the sick fish I did a small 20% water change, which I do every 2 weeks.

  • Temperature: 24.2 °C;
  • pH: 7.4;
  • KH: 6;
  • GH: 3;
  • Nitrite: 0.

Plants are growing fine, there is not much waste and I use liquid fertilizer. My tanks filtration is about 5 times an hour and lights are on for 9 hours a day. Algae growth is almost none, the algae that do grow are most of the time eaten by 5 shrimps (soon to be expanded by a pregnant one).

Both the water quality and environment did not change in the past weeks.


I feed two times a day. I try to feed small amounts, but I'm suspecting that I could feed them less. 2 times per week I feed them with frozen food.

Actions taken:

Because I didn't notice any disease that could possibly be cured with medicines I didn't use them. But I did add some salt (0.05 grams of 99.8% NaCl per liter of water) to the water to give the fish a more friendly environment. This helps because the fish spends less energy getting salts out of his body (osmosis etc.).

Two days later:

Now two days later the fish seems more alive and tries to eat when feeding. Also the breathing is way slower than before (back to normal). But the fish still swims without using the tail fin. Could it be paralyzed for good?


What kind of disease could this be?
What causes a tail fin to suddenly stop working?

I should notice that one of my other Norman's lampeyes misses an eye (ironically), I discovered this just after I got them from the pet store. But it seems that it doesn't bother the fish, he is doing fine.

Could these fish suffer from inbreeding?


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