Question
Hi,
Have had a 200 gal pond for 2 years...several shabumkins, 1 koi...no problems until today.  started feeding winter diet about 2 weeks ago it was cool.  Now have heat wave been in 80's last 3 days.  got up today all dead....help.
chuckie

Answer
I'm so sorry about your fish!  The food probably was not a factor.  Did the fish have any symptoms or did they just up and die?  I would check the water's pH, hardness, ammonia, nitrite, nitrate, and oxygen levels to rule out those problems.  

This page on my site lists reasons fish might die:
http://www.fishpondinfo.com/health4.htm#why

When the entire pond dies quickly, it's usually due to bad water quality or poisoning.  Is there anyway pesticides, bleach, or other toxins could have gotten into the pond?

Since they're all dead (are other animals like frogs dead too if you have them?), I suggest completely cleaning out the pond and putting in fresh water just in case the water was toxic.

I hope things work out.  Again, I'm sorry for your loss.