"Jules59 via PetKB.com" u25279@uwe wrote in news:660be06df6350@uwe:

does anyone know what causes a fish to swim in circles with it's nose
to the bottom? obviously it's in distress, in fact I'm sure it's
dying, but is there any danger to my other fish? Is this contagious?
Help--this is my first tank.

What you are seeing is a symptom which could potentially have many
causes.

An advanced internal F. columnaris bacterial infection can cause this
symptom. Do you see any large whitish patches on or just beneath the
fish's flesh? This disease is not really communicable, but the poor
living conditions required for an infection to take place are common so
the disease may affect more than one fish.

Fungal infections, such as Ichthyophoniasis, can cause this symptom as
well. Do you see any darkening of the skin, does the flesh look rough,
or does the fish appear to be emaciated?

A variety of internal parasites that damage muscle or nerve tissue can
cause this symptom as well.

Ichthyophoniasis is communicable as are most parasites.

I could have been ammonia poisoning. Ammonia (not ammonium) is capable
of crossing the blood-brain barrier to destroy nerve tissue.

For lack of any other symptom it could have been something like a
stroke, or just the last desperate struggle of a weak fish near death.

If you cannot observe any other symptoms besides the crippled swimming
pattern your best bet is to test your water quality... even if there are
other symptoms that would be a good place to start anyway.

If this is your first tank and it is still rather new my first suspect
is ammonia poisoning.

If your tank tests clean then I would suggest removing the dying fish to
reduce the possible treat of transmission of any unknown pathogens.
Many parasites and internal fungal infections are believed to be
transmitted through injection of infected tissue.