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Danio lip rot


AC Members
I have a few Danios with this weird lip growth. None of my other fish have had it. It’s white and kind of hairy looking. Any help is greatly appreciated!

Here’s the time line:
  1. Set up a 55 gallon tank with 11 danios and 5 corys
  2. I did every other day 10% water changes and testing (all levels safe)
  3. Suddenly a danio gets this weird lip growth
  4. After about a week the danio kicks the bucket and I noticed 2 more getting the growth
  5. I brought a water sample to the pet store and they said it was bacterial and my tank is in stage 3 of cycling.
  6. He said don’t change your water for a week and bring another sample
  7. A week later, the new growths disappeared and the pet store said my water looks good
  8. Since then (about 3 weeks) I’ve added 4 more corys and 6 platies (each on different weeks all quarantined)
  9. Now the growth is back on 2 of the fish
I’ve been doing some additional water changes since adding the new fish. Could that be it? Am I throwing out the good bacteria?



AC Members
Water changes don't remove beneficial bacteria. They are on all tank & filter surfaces.

Did you "cycle" your tank before getting fish? What are "safe levels"? Any ammonia or nitrite is harmful to fish. It's good you're doing daily water changes but try to do larger 1s, 30-50% if you can.

I think your danios may have columnaris. There seems to be 2 forms, a fast moving 1 that causes red ulcers & death in a couple days. & a more slow growing type. It's 1 of those bacteria that can be present & at low levels doesn't cause issues...unless there's other stress in the tank (like ammonia). Water changes can help, as can keeping your temp in the low 70Fs. All you fish are quite happy at that temp. I would NOT treat with an antibiotic (yet anyway), as it may interfere with cycling.

Good luck!


AC Members
Thanks for the recommendation! The ammonia was a bit high so I did a 50% water change and all is well now.


AC Members
Keep doing daily WCs! No amount of ammonia is "safe". Keep testing! WCs can only help...

& let us know how you're doing in a few days or weeks. It's hard work to do daily WCs , but you need to.