It would like to take a net from nylons and find out if there are water "fleas" in the water (they catch fish in the aquarium), if so and if there is sufficient access to sunlight in the pond, about 1m3 of water will feed one fish. also on whether it is so-called. It is possible to feed grain, but it is good to feed on some hard mat in the water to check if it is eaten so that it does not start to rot. Here, too, less is more. It is good to know what Ph has water - the optimal is around 5.5. The pastry does not matter, but it is better to feed it when it is warm, the fish is scattered and collects even from the surface. (water inflow, water movement - ice cutting), If the pond is about 1.7 m deep and has a non-freezing inflow, you don't have to worry about oxygen. Finally, one piece of advice - if the pond has a drain device - for the winter - it is good to cover it with five bottles at the point of contact with the surface - straw used to be used so that the ice would not pull it out.