koi are dying fast

Question
I have 4300 gallon outdoor pond. I have noticed that my koi skin are turning pinkish and the fins have blood streaks.
  The only thing I did was keep adding agaefix every 3 day and drain the water and add some more. Then I notice my gold fish are not effected by this. I don't know what to do now but keeps draining the pond just in case if I overdose my pond and maybe that's the reason they are dying. most of them are about 12 to 16 inches long I have them for 8 years. please help!

Answer
I'm so sorry that your fish are dying.  The blood in the fins is septicemia which can be caused by poisoning, water quality problems, or bacterial infections.  AlgaeFix is usually pretty safe at the recommended dose.  If you had a lot of algae, when it died, the oxygen levels could have gone done to dangerous levels.  Is th epond well aerated?  Where the fish gasping?  How much water did you change?  Did you add dechlorinator with the new water?  I would be sure to aerate the water well, maybe do more water changes (with added dechlorinator and maybe some pond salt).  If you suspect other poisonings, then add some fresh activated carbon to the filter.  I hope your remaining fish recover!  Good luck!

Robyn
fishpondinfo.com