Goldfish are best kept not in bowls but in a natural habitat--a self-sustaining outdoor pond with clean, clear water that provides the balance for both fishes and plants. Housed in a pond, goldfish can have adequate space for swimming and they can feed on a nutritious diet of live invertebrates, algae and assorted vegetation. Transferring goldfish from an indoor aquarium to an outdoor pond is simple but a few precautionary steps have to be followed.
Condition the pond water. A newly constructed pond must be cycled before introducing any fish. The water should be conditioned with a de-chlorinator solution and the beneficial bacteria allowed to grow over a period of 2 to 3 weeks.
Test the pond water. Use a water testing kit to determine if the water is already cycled and safe for fish. The ammonia, nitrite and nitrate readings should be as close to zero as possible; if any of the readings are high, the water is not ready.
Check the water temperature. Avoid shocking the fish with a wide disparity in water temperatures. The closer the temperatures of the aquarium and outdoor pond, the better.
Transport the goldfish with care. Place aquarium water in a bin. Then catch the goldfish from the aquarium with a net, place them in the bin and take the bin to the pond area.
Lower the bin into the pond water and coach the fish to swim out of the bin.
If the water temperature of the aquarium is vastly different from the pond, float the bin containing the fish for several minutes on the surface of the pond to equalise the temperatures. If introducing goldfish acquired from a pet store, float the plastic bag holding the goldfish into the pond for 15 to 30 minutes. Open the plastic bag and net the fish out of the plastic bag. To minimise contamination, do not pour the water from the plastic bag into the pond.
Do not overcrowd goldfishes in the pond. The rule of thumb for ponds without a filter is no more than 2 inches of fish for every 1 square foot of pond surface area.