goldfish in a pond

Question
QUESTION: i keep finding 1 dead goldfish every day in my pond a was woundering wot it could be that makes them dye

ANSWER: HI Michelle,

Is the filtering system working properly?

Have you changed the amount of food given to them?
Have you introduced anything new to the pond, such as plants, fish or any other living creature?
Have you noticed any foam on the surface of the water?
Please answer these questions and I will be able to give you a better answer.

Carlo

---------- FOLLOW-UP ----------

QUESTION: Yes the filtering is working propely
no i have not changed the amount of food
there is nothing new in the pond
there is no foam on the services
when i feed my fish thats in the fish tank they all swim to the top straight away and eat the food but the ones in the pond don't. and i feed them pond fish food

Answer
Hi Michelle,

Maybe bacteria could be attacking your fish.
In any case, there is something that you could do that would not harm your fish, and help you rid them of any possible contamination:

 Remove all the fish from the pond and place them in a "hospital tank".
Drain the pond and wash it with water and salt(3 kilograms of salt per every 100 liters of water)
Rinse it well, fill it up with water and wait a few days. After that, add salt to the water of the "hospital tank" (250 grams per every 100 liters of water) leave the fish in there for about  4 hours.
Put them back in the pond.
Make sure that the water temperature is the same (hospital and pond)

Before you do it, examine the fish, and let me know if you find anything
unusual

Good luck!

Carlo