Garden Pond Option: Fish Ponds vs. Water Gardens
Koi Pond
A koi pond or fish pond will require slightly more effort to maintain than a garden pond. This is because fish require adequate filtration and aeration to survive. A koi pond is different from a water garden because there are restrictions as to what types of plants you can use; koi eat certain types of plants (wuch as Water Hyacinths and lily pads). Because plants are an essential part of the fish pond's eco-system, consider adding a separate section (just for plants) to the koi pond that the fish cannot swim to (E.g. an upper pond where the water circulates before it returns to the main area).
A koi pond should be larger than a water garden because koi can grow quite large. It is recommended that a koi pond be no less than 1000 gallons in volume. To keep fish over winter, a deep spot must be planned within the fish pond that will go just past the frost line in your area of the country. The deeper section of the fish pond only needs to be large enough to accommodate whatever fish and plants you would like to keep in the pond during the winter. The frost line in the United States varies from 3 feet to 5 feet deep. Please contact local sources to determine the frost depth in your area.
You will have to aerate your koi pond to allow fish to breath. A return of water through a pipe may not sufficiently aerate the pond during times when an increased oxygen supply is required. A fountain that spits water back into the fish pond should provide the fish with an adequate source of air. Insure that aeration is increased at night, when you add chemicals to the water, and during extremely hot days.
If you're considering a fish pond, pond filtration is paramount! Looking for filtration for your fish pond? Check out Gardensupermart's complete line of pond filters.
Water Garden
A water garden is much easier to set up than a fish pond or a koi pond. A water garden can contain plants, waterfalls, garden fountains, and a pump to circulate the water. If murky water does not bother you, then you have no need for a filter.
Water gardens in moderate climates usually need for an area of the pond to be at least 2 feet deep. Colder climates require a depth to of at least 12" to 16" of water below the freeze zone.