Deformed zebra danio

[French]

Hey, anyone ever come across a deformed/injured zebra danio? I have one that looks like it has had its back broke and healed over a little more then halfway Down its tail. Could it be from excess ammonia levels?
Currently ammonia 1ppm
Nitrite 0
Nitrate 10ppm
PH6.8
50gal tank
Fluval C4 hob and Fluval 206 canister filters
Also using clear FX PRO for media in the 206.
Thanks

 

[Thumper828]

Ammo is really high. Do Water changes to bring it below.25. mathematically a 50% water change would reduce ammo to .50ppm ect.............