Owning fish can be the pinnacle of having a pond and add an extra dimension to pond keeping, but fish can put a massive strain on a nature pond’s balance. In a naturally formed lake there may be shoals of fish, but these fish will be very sparse and will only eat what nature provides.

Not only may the pond’s natural balance be altered by keeping fish, they will also affect the garden’s ecosystem. Many fish are active predators and could eat tadpoles or insect larvae and may denude a pond of any other wildlife.It is advised that large fish, such as Carp or Sturgeon, are not kept in a nature pond. Goldfish are non-native ornamental fish and are also not normally kept in a nature pond.A few smaller indigenous fish such as Gudgeon, Rudd and Tench are better suited, if you wish to keep fish in your nature pond.Pond fish in a nature pond can be fed shop bought foods, but these should only be given very sparsely, maybe a small amount once a week, and only to supplement a natural diet. If too much food is added, the pond’s natural balance may be adversely affected and the water quality will begin to decrease.

You should only add fish to a pond which has an area of deeper water. It is advised that a depth of at least 60cm should be provided to offer an insulated bed of warmer water and give the fish refuge during the colder months.Fish should only be added to a nature pond which is well established. There addition should be much more gradual than in an ornamental garden pond, and the stocking rates should be much less, especially if you opt to keep the pond unfiltered.For a guide to adding fish to a pond click here.For a general stock rate calculation for ornamental ponds click here.To calculate an adequate filtration flow-rate click here.