Goldfish are diggers and will scatter the fine sand onto leaves, injuring thin and less hardy plants, particularly fine-leaved varieties. They often dig in the gravel and can uproot plants or damage their stems. Plants grafted onto rocks or wood (e.g. anubias, java fern) are good choices.
Fancy goldfish, need a tank free of active or aggressive fishes, they require optimum water conditions to prevent fin damage and deterioration. They are best maintained at around 65°F (18°C); they may be susceptible to fungal infections and fin rot if kept at low temperatures for prolonged periods.
At higher temperatures the water should be kept well-aerated. Goldfish can tolerate the temperature itself quite well, but may suffer due to lack of oxygen.
If you wish to grow your goldfish a higher protein diet will also result in a faster growth rate. Where goldfish are kept in small or unfiltered aquariums, it is not recommended to give high protein food.
Feeding your goldfish a small amount at several times during the day is preferable to feeding one big meal. Goldfish are one of the hardiest of all types of fish, and are able to withstand a wide range of water conditions. However, the ideal pH is neutral to slightly alkaline (around 7.5), moderate hardness, and a temperature of between 60°F (15°C) and 75°F (24°C).
Foods designed for goldfish are usually lower in protein and fat than tropical foods, and made with a fairly high content of vegetable matter. It is generally recommended not to give goldfish too much protein, as this can lead to constipation and intestinal problems.
To avoid dietary problems, it is a good idea to include shrimp-based frozen foods and vegetable-based foods as a supplement. Only In fancy varieties a higher level of protein is desirable as this encourages the development of the fleshy head growths in Oranda and lionhead/ranchu varieties.
Goldfish like a tank with plenty of swimming room and are not particularly fussed about the presence or absence of decorations. They will do well in a 30 gallon or larger tank with a fine gravel bottom and hardy, cold water plants.
Making partial water changes on a weekly basis is the best way to keep your fish healthy, use an aquarium siphon hose to vacuum your gravel, remove leftover food, fish waste, and other organic material.