As I remember, the food goes through the koi quickly. I would guess
most anything would work in the short run...even nothing as they will
eat algae. Another order for a small time could certainly end up
wasting food.

Around here we have fed our koi catfish/trout food for about 15
years. They are doing well and growing. I recognize that folk differ
A LOT about the OK-ness of doing that. Years ago it was pointed out
to me that catfish food could cut their lifespan by 20% as they could
get fatty livers. Our koi are the inexpensive kind (Pet Smart, Wal-
Mart and donations from friends). I am scot enough that I hate to
spend a ton of money for 10 fish worth $4 each. Catfish food has gone
from $11 per 50# sack to $13 per 50# sack. A sack lasts a season more
or less. The koi can last 100 years! 20% would still put their life
spans way beyond ours (Phyllis and I are 66).