Question: What makes the frilly hairs on their gill dissapear leaving only bare stumps?

[stevenwignet]

I have 4 axolotls , 2 are in each tank. they are all healthy and eat/swim and interact fine with each other but have noticed that all the frilly gill hairs have all gone and all they have is the bare stumps of their gills.
they do not seem bothered by this and do not go to surface for air more than they normally do. the water is clean so no problem there either.

what makes the frilly hairs on their gill dissapear leaving only bare stumps?

 

[Boomsloth]

Sometimes nitrite and ammonia will burn them off but if they lost them it can take a bit for them to grow back. Do you have a lot of aeration in your tank?

 

[stevenwignet]

Sometimes nitrite and ammonia will burn them off but if they lost them it can take a bit for them to grow back. Do you have a lot of aeration in your tank?

water is fine and does not have any extra stuff like air or filters
they just lost all their frilly gills leaving only the stumps
they not struggling for air as they rarely go to surface and not having frilly bits does not seem to cause them problems

 

[Boomsloth]

How often do you do water changes? What are the actual levels of ammonia, nitrite, and nitrate? My guys lost most of their gills (melanoid lost all) to fungus a while back and by fixing the temp issue and doing water changes frequently they are all healing but the frills have grown back first.