koi and golfish dying

Question
Hi Carlo,
All my pond fish are dying.  I had about 25 total fish.  I only have 3 left.  When
they first stopped eating and noteced things wrong, I was told to use melafix
and pimafix.  I rotated them every other day.  My fish all continued to die.  I
have two goldfish left, and one very large Koi.  All he does is gasp for air, and
swims every now and then.  Two goldfish are doing the same.  When my fish
started dying I noticed that there was alot of blood on the surface of their
bellies and fins.  Some had cotton like bodies.  some had cloudy eyes.  My
two goldfish left that are white are turning pink to from the blood to the
surace.  My two foot long Koi looks pretty good, except gasping at the
surface.  Mouth and fin are working very hard.  This is very depressing and I
have worked to hard to find help and can't seem to get it.  I was told to find
the injection for the Koi.  I can not find that from anybody.  I wish I could
save him.  All pond levels are find and water is clear except for algae on the
sides and hoses.  I have a biofilter, and uv light, and two pumps just going
with hoses attached to help put oxygen in water.  I don't know what else to
do.  I have had my Koi for 8 years and never had a problem.  I already lost a
few days ago my other big Koi (his friend) for 8 years.  I was just hoping that
maybe you had some suggestions are know what I'm dealing with, it's
terrible.  Thanks, kathy

Answer
Hi Kathy,

This could probably be a sign of overcrowding.
There is a disease called Cottonwool Disease.
I would recomend you giving your fish a salt bath.
Use 3k kilograms of salt per 100 liters of water.
The fish should be put into it, and left for no more than 10 minutes.
After that, they should be kept in a hospital tank while the pond is thorughly desinfected.

Good luck


Carlo