fish pond...fish dying

Question
I recently started a fish pond around 250 gallon.  Started with 3 fish, 2 comets and a koi.  They were doing well and added around 13 more goldfish and koi to it.  I had these for 7 days before they started to die.  I lost 4 so far and believe a 5th is dying.  They have no apparent spots or anything on them.  The only sign of sickness is they start to swim on their sides and within very little time they die.  Please help I don't know what to do!! Should I try salt for fish in the water or bacterial treatment?????

Answer
The cause of your problem is either high Ammonia or low pH, or both.  Test both of these and if either one is out of balance, perform a 50% water change.  I recommend only adding 2 to 3 fish at a time, and only adding fish once a month at most.  Also, do some research on how many inches (or pounds) of fish you are supposed to have in a pond of a certain volume.