How many pond zones does your pond have?
„Only one - and it’s filled with water“ might be your response. But there are innumerable advantages to having your pond split into different zones. Let’s start with the shallow water: a shallow water zone gives a lot of marsh plants the opportunity to grow upright in the water, to withdraw nutrients from the water (so that the algae die of starvation) and saves them from being gnawed by plant-eating fish. In these marshy zones a lot of beneficial bacterial degradation processes also take place, to keep your pond clean and clear.
The pond bottom often slopes down towards the deeper areas. Gravel is then unable to settle on the slopes and even small stones slide down. A terraced structure can help here.
The deepest point should have a depth of at least 180 cm in countries with harsh winters. In this deepest area the water will not drop under 4 °C, since water has its highest density at 4 °C. Your fish can hibernate here, no matter how thick the ice cover above is.
For larger fish it is advisable to build steep pond walls with the upper slabs reaching to the edge or over the edge of the water to give access. This will also provide an ideal spot for fish feeding without them having to slip around in the shallow water, damaging the mucous membrane on their bellies. You’ll be able to kneel right at the side of the pond, feeding them individually by hand. This will make it easier for you to catch a fish at a later date, if it should fall ill, etc.