The stocking level of the pond is critical to the health of your fish. Too many fish leads to decreased oxygen levels and the extra fish waste leads to ammonia and nitrite build-up. To a certain degree, your fish load can vary based on your level of filtration. A pond with an undersized filter will not be able to keep as many fish, while an oversized filter will allow you a few extra fish. With an average-sized filter, your preferred stocking level will be based on surface area of the pond. For goldfish you can keep one average size fish for every 3-4 square feet of surface area. For koi, it should be limited to one fish for every 10 square feet of surface area. For example; a 10 x 10 pond will have a surface area of 100 square feet (assuming that it is a perfect rectangle). With an average filter this pond could house up to 30 goldfish or 10 koi. Of course, keeping fewer than this would make keeping good water quality even easier. It is also important to ensure that the water is suitably aerated. Aeration can be added via a waterfall, fountain or aeration pump.

It is important not to stock new ponds too quickly. New filter systems take up to eight weeks to mature and during this period, Ammonia and Nitrite levels will fluctuate dramatically. If you introduce too many fish at once, you will risk their health.

There are two main aspects to properly feeding your fish. These are feeding the right foods and feeding in the right amounts. Each time you feed your fish, whether its three times a day or three times a week, you need to make sure you feed only what they can eat in 5 minutes. A little experimenting can teach you how much to feed. If, five minutes after feeding, there is still uneaten food you know to not feed that much next time.

Determining what and how often to feed your fish depends primarily on water temperature. In warmer water (15 to 25Deg. C.) the metabolism of the fish is high and they can be fed 2-4 times per day. At this time you should be feeding a food with a high protein. In spring and Autumn when your water temperatures fall to 10 to 14 Deg. C, you should reduce feeding to once every 1-2 days and feed a low protein food. When the temperatures drop to below 10 Deg. C. stop feeding the fish. On warm days the fish may become active and "beg" for food. Don't be fooled. Stay strong and do not feed. If the fish do need a little food, they will find enough growing in the pond. These cold temperatures slow the metabolism of your fish and food will not be properly digested. It can take 3-4 days for the fish to digest it. It's not worth the fish's life to give it food.

Water quality is very important to the health of your fish. Poor water conditions stress fish. A stressed fish is more susceptible to disease. One of the most important things for water quality is to make sure toxins are not getting in the water from fertilizers or pesticides. Don't spray anything near the pond and make sure rain run-off does not flow into the pond as this can carry these very toxic chemicals. Some of the other factors in water can be tested, such as pH, ammonia, and nitrites. A pH level of 6.6 to 8.4 is safe. The idea range is 7.0 to 7.8. If it becomes necessary to adjust the pH it should be done gradually as a sudden pH can cause severe damage. Ammonia should be zero. Any level of ammonia can be a problem. Note that ammonia is more toxic in higher pH ranges. The nitrite level in your pond water should also be zero.

If your ammonia or nitrite level is high it tells you that you either have too many fish or your filter is not doing its job adequately. Another possibility is that your filter may not have had time to cycle if it is a new pond. As with a new pond, a filter that has been shut off for the winter will need time to mature. This can take several weeks. A partial water change should be performed to dilute the high ammonia or nitrite problem during this time. It is best to set up a regular routine of water testing.

It is as important to look after your pond and its inhabitants in the winter as it is in the summer. The vast majority of fish deaths that occur during the winter months are avoidable with a few simple rules.

1) Never feed your fish when the water temperatures are below 10 deg. C. as food can remain undigested in the stomach and cause infection.
2) Always turn off your filters or raise the pump well off the bottom when water temperatures drop below 10 deg. C. Ponds that are left still will stratify and the water at the bottom of the pond will stay constant and safe for fish.
3) Always make a hole in the ice during prolonged cold spells to aid gaseous exchange. This is best carried out with hot water or a floating pond heater.
4) Always remove as much organic waste from the bottom of the pond in the Autumn to prevent Methane build up during freezing weather.
5) Leave your fish alone! Disturbing your fish during cold weather is a very quick way to kill them.

No matter where you buy your fish, how they are treated before purchase is exceptionally important for your existing fish as much as it is for the new arrivals themselves. The average fish in a Pet Shop has been shipped from another country via a flight and through customs to a fish wholesaler. It is then kept in tanks pending sale to the shop, when it is boxed up again and delivered. It is then unpacked and housed, often in cramped conditions, with other fish from other sources, ready for a customer to select it. When selected, it is then re-bagged and you take it home.

Buying a fish direct from the farm means that the majority of this stressful process is completely avoided. The fish will come straight from the farm, to your door. There is no chance of any cross-contamination with other fish from other sources and the fish arrive relatively stress free. It is always advised that all new fish from any source are kept separate from existing stocks until you are 100% happy with their health and condition. However, in the vast majority of cases, this is not practical and fish are introduced immediately into the pond with the existing occupants. It is in this situation that buying from a reputable farm or supplier is most important.