In any kind of pond, but especially small ponds it is important to not exceed the
capacity of the biofilters to remove wastes so the fish are not exposed to either
ammonia nor high levels of nitrates. Typical biofilters are very temperature
sensitive peaking around 80oF or so. Lower than 60 and the bacteria slow down. This
is not true for plants in veggie filters however.
The type of food given GF and the amount at one time is going to affect wastes. GF
and koi do not utilize carbohydrates, so it is in one end, out the other and is waste
in the pond that must be broken down. The higher the content of carbs in the fish
food, the more wastes. GF typically nibble all the time and that gives their gut
time to process the food and poop out small residue. GF given large meals, or, dry
meals and GF have NO stomach so the food moves directly to the intestines and move
thru rather fast without as much digestion. Again, more wastes in the water.
Bacteria work on carbs, but not so much on proteins.
So as cold weather/water approaches I feed freeze dried krill exclusively. I set up
my "in pond" veggie filter and shut off water to the big one. When that happens I
have to cut way back on how much I feed as well. After the first freeze I cover my
pond and drop in the 500 watt heater. I feed small amounts of krill every few days
as long as the koi come up to feed generally when the temp is 50 or better. I am in
Wisconsin due north of you and it used to be the fish went without food for 6 months
of the year. With the heater, the plastic and some kind of filtering there is only
one month a year they go without eating. Ingrid

On Tue, 9 Sep 2008 18:56:33 EDT, emceemc wrote:
I have a small pond with currently 5 medium goldfish in Chicago.
I could feed them the same as always, begin to wind them down with
progressively smaller feedings, or feed them more to fatten them up
for the long fast until April.