Pinhole Fin Rot

[Essjay]

To clarify - the only 'fine' for ammonia and nitrite is zero; the only 'fine' for nitrate is less than 20 ppm.
There is no 'fine'; for pH, GH or KH as the levels we should aim for depend on the species of fish in the tank.

 

[Naughts]

Curling fins can suggest the water is hard.