Each fall I post this recommendation. Please consider covering your pond if
it is less than 5000-10,000 gallons and freezes over. Small ponds with many
fish may not freeze if they are 4 ft. deep but your fish will be very
stressed in the spring. Each year our local pond friends have several fish
that die from the stress. I have always covered my pond and in 4 years with
13 fish (52fish/years experience!) we have NEVER had a fish die.
Please look at my web site for a simple method and plans to cover your pond.
This is not a commercial trick but I do list some links to material
suppliers I have used. You are of course free to get materials where ever
you want.
http://pw1.netcom.com/~rbstamm/koidome.htm

If you want a good method to orally medicate one of two fish at a time check
this page out. It uses Cipro and frozen peas, works great and cheep!
http://pw1.netcom.com/~rbstamm/koi_medication.htm

Brad Stamm