Perhaps you can recall purchasing your first goldfish in a plastic bag at the pet shop. It was a tiny little thing swimming lazily around in a tiny bowl and seem content, or so you thought. Maybe you figured it would always remain small enough to live comfortabley in its new home. Maybe you didn’t realize it could ever get any bigger.
If this sounds familiar, then you’re like most new goldfish keeper. Most people think if they keep their fish in a “small” tank, the fish will never outgrow it. Wrong. Instead of outgrowing it, it’ll become stunted. And the key difference between a stunted fish and a healthy one? The key is time, space, and knowing what kind of goldfish you’ve got on your hands.
Why Goldfish Need More Space to Grow Big and Healthy
This chart compares size by breed. Size differences among breeds are reflected in the chart. Speedsters like common goldfish and Comets are long-lived, fast-swimming fish. Their streamlined body shape allow them to swim efficiently; one tail propels them forward. With their rapid metabolism, these varieties can grows to fourteen inches or longer in a pond due to available water volume.
Fancy types such as Ryukins or Orandas differ from common varieties because rounder-bodied fish with double tails aren’t efficient swimmers. That limits their maximum size to somewhere around eight or nine inches. Knowing that can help you understand that housing a comet in a tiny bowl is torture. It also shows that keeping an Oranda in a huge pond are overkill.
The initial growth period is rapid. You can tell what breed you have by the change from baby fry to an adult fish, all within the first year. Fin development occur. Color appears. By age three, most varieties are near their adult size and this is where things get tricky. Because growth doesn’t appear to continue, many people assume they’ve maxed out. They didn’t. A goldfish grows very slowly but continuously for decades. With proper care, a Common can reach 25+ years old and continues to gain a little length with every passing year.
As you can see from the timeline above, the majority of change occur in those first couple of years, however there’s still potential. Everything else follows the environment. Water quality is the one thing that is not negotiable. Because goldfish are messy (i.e., they produce large amounts of waste compared to body size), they require good filtration and frequent partial water changes. Chronic stress from ammonia spikes stunts growth.
Likewise diet also matter. A high-quality pellet contains enough protein for developing tissues. Most cheap flakes don’t contain enough nutrition for reaching their genetic potential. Temperature also matters. Metabolism operates faster in warmer water, resulting in faster growth in summertime. In cooler winter waters, everything slows down because it’s a biological rhythm that you can’t force.
People are confused about tank sizes, such as what 10 gallons means. Nothing! That’s plenty of room for a single fish, right? Wrong. At minimum, that’s what your fancy varieties should of had (twenty gallons), to allow them room to move around and to stabilize water parameters. Bigger tanks also dilute waste better. Ammonia spikes stunt growth and cause chronic stress.
For multiple fish, more space is required. Aggression arise from crowding. Disease spreads through crowding. The infographic visually shows how much space each really require to live well. Most folks underestimate by half.
The opposite is true in pond living. Hundreds if not thousands of gallons of water outdoors in your pond, gives single tail varieties ample opportunity to grow into their full genetic potential. Where you may have an eighteen inch long fish in a big garden pond, that same species will remain small inside. There’s no voodoo going on here. It is just biology reacting to what it has at its disposal.
Those fish we’ve read about being the largest in history spent decades outside in ideal conditions. They had clean water, good food, and space to roam around. Taking care of goldfish means more than just how they look at first glance. Their low cost tags don’t make them entry-level animals. Goldfish are smart, tough, long-lived creatures who deserve your respect.
Giving them proper accommodations avoids any physical damage caused by stunting. Feed them correctly so they can live to their fullest potential. A healthy goldfish swimming happily in a tank of clear water is worth more than keeping a cramped one ever will be. The latter starts as a small fish in a bag and ends as a companion for several decades if you know what you’re doing.
