Video Link: https://www.youtube.com/watch?v=k326_yiQG1s
Factors Affecting Growth Rate in Goldfish
All of the following factors go hand-in-hand. To realize a goldfish's best growth potential, all factors should be maximized.
- Temperature - Despite what some may tell you, goldfish are not necessarily "cold water" fish. Yes, they can survive and thrive in cooler temperatures than most aquarium fish can, but goldfish are tolerant to a wide range of temperatures and can live just fine in temperatures of up to 90 degrees Fahrenheit or higher (as long as there's enough dissolved oxygen). In warmer temps, the goldfish's metabolism is faster, so it will need to eat more, equating to faster growth. In temperate climates, goldfish experience a dormancy period in Winter where they're not eating or growing as much, followed by a growing season in Spring and Summer where they're eating more and growing faster.
- Feeding Amount - With a warmer temperature (and thus a faster metabolism), the goldfish will need to eat more. Eating more of course means faster growth. Feed your goldfish very carefully. If the goldfish is constantly eating only processed pellets, it's more likely to develop swim bladder or buoyancy issues. The more soft foods you provide (gel food, frozen brine shrimp or bloodworms, algae sheets, etc.), the better. Many small meals throughout the day are better than one or two large meals since goldfish are natural scavengers and also don't have much by way of a stomach to hold food while it's being digested.
- Water Quality, Water Volume, and Stocking Density - Poor water quality (which can mean excessive ammonia, nitrite, or nitrate, dissolved organics, high bacteria count, fluctuating pH, low dissolved oxygen, etc.) is almost always caused by not having a large enough volume of water for the fish and/or keeping too many fish in too small a space. If the fish is living in poor water conditions, it will never reach its growth potential. To maximize growth (and more importantly, health), water should be kept as pristine as possible.
Goldfish grow the most during their first year of life. After that; they continue to grow, but at a slower rate. Thus, if a goldfish experiences less than ideal conditions when young, it may never reach its growth potential, even if conditions improve when it's older.
Is Fast Growth Healthy?
Be very careful not to go overboard; you want a healthy fish, not an obese fish. Keep in mind that when goldfish consistently live in temperatures that promote growth and have a consistently higher metabolism, the life span tends to be shortened. This is not necessarily a bad thing, it's just the way their biology works. Even though the fish may still be as healthy as a slower-growing fish, higher metabolism generally means a shorter life span. Extremely fast growth is not required for your goldfish to live a happy, healthy life. Yes, some fish can become severely growth-stunted and remain tiny, which can lead to severe health issues. But generally, a smaller-than-average fish is not necessarily unhealthy. Many breeders maintain that it's good for their fish to experience a cooler dormancy period in which they are fed less. This helps them shed the excess weight they put on over the Spring and Summer and readies them for the next breeding season.
Is fast growth best, or slow and steady? Look at your goals and priorities for your fish and decide for yourself. Neither answer is inherently right or wrong since a goldfish can be healthy and happy either way.