koi are dying

Question
I have 4300 gallon outdoor pond.I have a "green pea soup" water no shade. I have been treating my pond with agaefix every 3 days with 20 % water change before adding more algaefix to kill the algae. Now my koi are dying and some have red blood streaks on fins and tails and others are pinkish in color. I'am really upset this is happening cause, I have this koi for 8-9 years. please help.  And I was told that maybe I added too much alagecide that "I'am poisoning" my fish.What can I do to solve this problem. And have been draining the pond to delute the pond water if infact I have too much alagecide in it. Any advice?

Thanks CarmenH
Orting, Wa

Answer
Hi,
judging by your comments that your koi have blood streaks on their fins and their bodies are pink the streaks are caused by stress and the pinky colour could be that they have been burnt by using to strong a mix of you algeacide which will have altered the PH of the water, I would suggest a massive water change,
George.