Question
We moved into our home in June of 2005.  The Koi pond (about 3000 gal) and 9 adult Koi came with the home.   The first year we were here the adult Koi spawned.  I gave away as many 1-2?babies I could catch but many were left in the pond.  I guess that we now have somewhere between 30 and 40 fish  including the nine adults.  It has been a struggle to keep the pond clean with all of the fish but we are managing until we can build a bigger pond (this one leaks) or make repairs.

It抯 cold here (below freezing a lot).  A few weeks ago we found one of the smaller Koi (about 6? in the filter.  Thinking it was dead we removed it intending to bury it.  When we saw it struggling to breathe we put it in a bucket of water for a few minutes while we filled one of the 50 gallon aquariums we have in the tool shed.  I added some salt to the water, one of the pond rocks with algae on it and let put him in.  He seems to have recovered and is a lot more active than the fish in the pond.  I have not fed him. The water in the aquarium (43 degrees) is about 10 degrees warmer than the pond.   He has been doing well in the aquarium for the past few weeks.  

A few days ago I found his 慴rother?(Fish #2) nearly frozen in the ice near the surface of the pond.  We removed him and found that he was still struggling to breathe.  He is now in the aquarium with Fish #1.  Unfortunately, he must have been mired in the ice for some time and there some abrasions to top and the sides of his head.  I began today to treat the aquarium with Meli-Fix today.  I hope this will help with his injuries but please stop me if I抦 wrong.  We are in day number three with Fish #2.  He does not seem to be responding as well as Fish #1.  

My main concern is that he lies on his side and I抦 wondering if this is healthy for him.  I know that small fish can do this (and often do in cold weather) with no ill affect but, when is a Koi no longer considered small?  Both are Butterfly Koi with Fish #1 being slightly larger than Fish #2.

Thank you.


Answer
Hello Jacqueline!
It is possible that the small Koi will recover over time (you have been doing a great job and pretty much all the right things), but it is just as possible that he will not.
I suspect that the Koi in your pond are starting to suffer from Oxygen deprivation. With that many fish competing for what little oxygen may be in the water this tends to become a real problem in colder areas of the country. This problem, more than any other, leads to large losses of Pond Fish in the Winter.
You have been doing great trying to save these two, but to prevent further Koi from getting into difficulties it would be best to add an aeration kit to the pond. They are relatively inexpensive and can help prevent the loss of Koi in the winter.