it depends on how much water is in your pond. 200 fish is a lot, and they produce a
lot of waste, use a lot of oxygen in winter under the ice. on rec.ponds the
recommendation is to keep an air hole open all winter AND use an air pump with a
couple big airstones to put oxygen in the water.
If your pond is open and leaves ill in over the years a lot of dead, decaying
material builds up on the bottom of the pond and the rotting uses up the oxygen in
the pond. it also produces toxic gases that can weaken and/or kill the fish.
there are critters that eat fish including mink, weasels, snakes, herons,
kingfishers, raccoons, owls, cats. But I think your problem is stuff in the bottom
of the pond.
one other thing, dont know how cold your water is, but koi, for example dont eat
until water hits 46-50oF. and if a predator has been to the pond fish will hide.
Ingrid

Kay la wrote:

We have a large pond and have 3 generations of fish which we feed
daily. Last year 10 surfaced in the spring and we assumed they died
of lack of air so this winter we made sure that air holes in the ice
were kept open. This year we have not seen one fish. NONE!! There
were about 200 fish last year. The neighbour put in a few bass one
year and they have multiplied over the years. How could that many
fish disappear without a trace? Would a snapping turtle clean out a
pond? The pond is about 50 x 100 feet. We are completely puzzled.

Lori



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