How to Look After Fish in a Garden Pond

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Pond fish need oxygen-rich water, nutritious food and protection from predators. Koi and goldfish are the most common types of pond fish. The amount of fish a pond can hold depends on how many gallons of water it holds. You can stock one inch of fish per one gallon of water.

If your pond holds 50 gallons of water, you can stock it with 50 fish that only grow to one inch long. If the fish get bigger than this, you must make the pond bigger or get rid of some of the fish. Too many fish means less oxygen and more waste.

Use a pond calculator to figure the number of gallons you have in your pond. You'll need to know the depth, width and length of the pond. There is a calculator in the resources below.

Purchase a pond filter that will cycle the total amount of gallons in your pond twice an hour. A 100-gallon pond should have a filter that pumps 200 gallons per hour (gph). Purchase a three-in-one filter that will do mechanical, biological and chemical filtration.

Set the filter up in the pond according to the manufacturer's recommendation. Some filters are set at the bottom of the pond and some sit outside the pond.

Change the chemical filter once every two weeks. It may need to be changed once a week, if the pond has a lot of suspended organic matter in it.

Inspect the bubblers at the bottom of the pond to ensure bubbles are coming out of them. The bubbler pump plugs into a power outlet and sits outside the pond. When the bubbles rise to the top of the water, they pop and oxygen absorbs into the mist. This mist returns to the water and oxygenates it.

Check to ensure the waterfalls are working properly. Look for leaks where water might be escaping the waterfall boundaries. The waterfalls should be churning the water in the pond to increase the oxygen-to-water exchange.

Check all spitters and fountains to ensure none of the water inlets have plugged. You may have to remove the pumps to clean the encasements of debris.

Set a floating heater in the pond during the winter months to keep a hole open in the ice. This will allow ammonia gases to escape from the pond.

Purchase a water-test kit that tests levels of pH, ammonia, nitrite, alkalinity, salinity, nitrate, dissolved oxygen, chlorine and water hardness. These kits can be found at a fish pond supply or pet store. Test the water according to the product's instructions label.

Remove 10 per cent of the pond's water once every week. If the pond contains 100 gallons, take out 10 gallons. Use a five-gallon bucket for small ponds. Use the pond's pump hose to pump water out of larger ponds. You would need to take 100 gallons out of a 1,000-gallon pond.

Replenish the pond with 10 per cent of new water. Add a de-chlorinator to the new water being dumped back into the pond.

Sprinkle onto a pond fish food high in protein during the summer months. Feed only as much as the fish can eat in five minutes. Remove any uneaten food with a leaf net. Do not feed fish when water temperatures climb above 29.4 degrees Celsius. Feed the fish twice a day when temperatures are between 15.5 and 29.4 degrees C. Keep a submersible floating thermometer in the pond to check the water temperature.

Feed a pond fish food high in carbohydrates during the spring and fall months. This will help the fish build up reserves to get them through the winter. Feed the fish two to four times per week when water temperatures are between 10.0 and 15.5 degrees C.

Feed the fish during the winter months only when water temperatures climb above 10 degrees C. If you feed a fish when temperatures drop below 50, the food will rot in the fish's digestive tract, because it won't be able to metabolise it.

Submerge a fish-safe hideout in the bottom of the pond to give the fish a place to hide during predatory threats.

Set up a Scarecrow to keep predators away from the pond. This device uses a motion detector to spray anything that moves with a jet of water. Follow the manufacturer's installation instructions. You can find a water Scarecrow at a fish pond supply store. You can also go online, open a search engine and type in pond or water Scarecrow.

Set up a net over the pond to keep out winged predators and waterfowl. Follow the manufacturer's instructions to set this up. Most garden or fish pond supply stores carry pond netting. Multiple online retailers sell it as well.