"old dirtbeard" wrote in message
...
We have a mature 800 gallon pond in Los Angeles,
CA (seven years old) with lush plant life, 24 hour
filtration, regular incremental water changes, etc.

Currently we have a five year old Comet (very
large) and two four year old Koi (about 16") in
the pond. Two weeks ago we placed three new
comets, two fingerling Koi and ten minnows.

There could be a couple of simple reasons why your new fish are not making
it - either they were not healthy in the first place or the water in your
pond is very different to the water they have been used to. With the volume
of water you have your pond is really quite heavily stocked now anyway -
have you tested for Ammonia/Nitrites? It may well be hat you have levels of
these which are enough to kill the smaller fish but which the bigger fish
can withstand (that said it wont be good for them generally). When you do
your water changes are you using a dechlorinator? Do you know if you have
Chlorine or Chloramine in the water? Chlorine (and Chloramine) will kill
off your bio filters to some extent.

My biggest concern is about quarantine. You have grown 3 nice big fish & it
seems very "brave" of you to just introduce new fish into the pond without
quarantining them for a couple of weeks first - I wouldn't be doing that
myself!

I