There are many myths and mis-truths in the fishkeeping world, one of the most common being: “You can keep goldfish in a bowl, because they simply grow to the size of the container.”
A good number of us at some point had a goldfish in a small unfiltered bowl as a kid. Maybe it was won at a fair, maybe it came from the pet store for 99 cents. It lived a year or two, often far less. Eventually it died because goldfish do that. They’re fragile creatures, and just die for no reason.
Well, that’s myth number 2: Nothing could be farther from the truth!
Let’s break down these common misconceptions and examine each part. Then we’ll tell you how to do it right.
- Myth: Goldfish Can Live In A Bowl
- Myth: Goldfish Grow To The Size Of Their Tank
- Myth: Goldfish Die Easily And Just Don’t Live Very Long
- Let’s Do It Right
- Goldfish Tank Size Requirements
- We Also Recommend Longer And Lower Tanks
- Water Quality
- Enrich Their Environment
- Final Thoughts On Goldfish Tank Size Requirements
Myth: Goldfish Can Live In A Bowl
Think of it this way. You could get a puppy and lock it up in a small kennel. Feed it twice a day and never let it out of the kennel again. The dog would likely live for years, but it would be a sad and stunted creature.
No one in their right mind would ever do this, so why would you do it to a goldfish?
This is the difference between “survive” and “thrive.”
The goldfish (or puppy in our example) can certainly survive for a time in a small and dirty environment. For the animal to truly thrive, it needs much better conditions. The puppy needs to run and play and get sunshine. The goldfish needs room to swim and clean water to live in.
Goldfish are extremely hardy creatures. They’ve been known to live for years in terribly poor conditions. Even subjected to stress, cramped quarters and filthy water, they still manage to muddle along. This is a testament to the fish, not the fishkeeper.
Just because they can survive, doesn’t mean they should be subjected to this kind of treatment.
Myth: Goldfish Grow To The Size Of Their Tank
This one is interesting. Goldfish actually do grow to the size of their tank. Anyone who’s kept a goldfish in a small bowl will testify that the fish stayed down to an inch or two.
Yet put that same fish in a 55 gallon aquarium and it could have grown upwards of a foot long! On the surface, this seems like the most accommodating fish in the world. In reality, a small bowl is stunting their growth.
Think again of our poor puppy. If it’s not allowed to run or even stand up all the way, it will become stunted and small. The kennel will be filthy and the dog will become diseased.
Similarly, the goldfish in a bowl isn’t being allowed to grow to its full potential.
Goldfish have been shown to produce a growth-inhibiting hormone when put in stressful conditions. There is debate as to why they have this ability, but experts agree it’s not a healthy thing to force them to do.
Some people even say that while the fish stops growing, their internal organs do not. They will continue to swell inside the fish, finally running out of room and causing an early death. We haven’t been able to find any hard evidence of this, but it’s as good a mental image as any to convince us to give our goldies the room they deserve.
Myth: Goldfish Die Easily And Just Don’t Live Very Long
Many people consider goldfish delicate creatures who just up and die for no reason. In fact, goldfish can live for decades! The healthiest of goldfish can be expected to live for 20 or 30 years. The oldest goldfish ever recorded was claimed to be 45 years old when it died!
If treated properly, goldfish will likely compete with tortoises and parrots as some of the longest lived pets you can own.
For this reason, goldfish should be considered a commitment, not an idle curiosity to keep around for a little while. There are plenty of other beautiful fish whose natural lifespan are only a few years.
Let’s Do It Right
We’ve learned that goldfish are hardy creatures who need plenty of space and clean water to truly thrive. So what should we do to give them the best environment possible?
Give them just that! A nice big tank resulting in room to freely move around and act naturally, in good quality clean water, with their environment enriched by a few decorations and plants.
Goldfish Tank Size Requirements
When it comes to goldfish care, tank size is one case where bigger is always better.
A 150 gallon tank may seem huge, but keep in mind the smallest natural ponds are many times this size. A slow flowing river may have that much water going past a fish every few seconds.
For consideration of goldfish tank size, there are two kinds of goldfish; fancies and commons (also known as single tails). There are plenty of differing opinions and schools of thought out there, but this is what we hold true.
The rule of thumb is as follows:
- For fancies, 20 gallons of water for the first fish, plus 10 gallons per additional fish.
- For commons, 30-40 gallons of water for the first fish, plus 12 gallons per additional fish (ponds are actually best).
This may seem like a lot at first. Keep in mind your fancy goldfish will grow to around 8 inches, and the common single tail goldfish can reach 10-12 inches. Rare cases have been recorded of common goldfish getting even larger.
They need plenty of room to swim and forage around the tank. The minimum length of a tank is 3 feet for fancies and 4 feet for commons.
We Also Recommend Longer And Lower Tanks
This allows for more surface area for oxygen exchange, as well as more length for the fish to swim in. A tall narrow tank might technically have the necessary volume, but wouldn’t give the fish much room to swim.
You can get away with a smaller tank when the fish is little, but you will need to upgrade soon. In the proper environment your goldie will grow very quickly, reaching full size in approximately two years. If you wait to upgrade the tank until absolutely necessary, you’ve likely already stunted your fish’s growth.
Larger tanks are actually much easier to care for than smaller tanks. The greater water volume means it will be a much more stable environment and will require less work to maintain. Imagine spilling a cup of coffee into the tank. In a 100 gallon tank, it’s a problem. In a 10 gallon tank, it’s a catastrophe!
Speaking of water quality…
Here’s a fun fact to tell your friends: ‘Goldfish don’t have stomachs!‘
They don’t actually store any food at all. Anything they eat literally goes straight through them. Because of this quirk of biology, goldfish produce A LOT of waste. They will dirty the water quickly and can easily overwhelm the biological filtration in your tank.
But the larger the tank you have, the less concentrated this waste will be!
Goldfish creating so much waste is also why filtration is so important in their tank. We prefer to double the amount of filtration the manufacturer recommends.
All filters sold at the live fish store will have a gallon rating on the box. If you are keeping a 40 gallon tank with a couple of fancies in it, we recommend at least 80 gallons worth of filtration. Like tank size, it’s almost impossible to have too much filtration in your tank. The only issue you might encounter would be too strong of a current from a canister or a hang-on-back type filter.
In addition, water changes are very important in goldfish tanks. We recommend 30-50% changes at least once a week. A good motto is, “When in doubt, change the water.”
Enrich Their Environment
There is an old myth that goldfish have a 3 second memory (There’s so many myths eh?!). Supposedly they never get bored because they don’t remember they’ve seen it all before. “Hey look, a castle! Hey look, a castle! I wonder what’s over here…hey look, a castle!”
In fact, goldfish have been shown to have a memory up to 3 months long. They even recognize faces and get to know their owners. So spice up their tank!
Add some decorations, driftwood, even some suitable plants. They will appreciate having a more interesting and engaging place to explore. This will also allow them to act and behave more naturally, foraging and investigating areas in different ways, thereby enriching their lives.
Final Thoughts On Goldfish Tank Size Requirements
So now that we’ve dispelled some of the most common goldfish myths you should know NEVER to keep them in a bowl!
Make sure your goldfish have plenty of water and plenty of room by buying for them a nice, big tank, and keep that water sparkling clean.
It may seem a bit daunting at first, an expensive tank and weekly water changes but tanks really aren’t that expensive and once you learn a routine, it really is a simple task and the rewards of a healthy and beautiful fish are more than worth it.
Happy Fish keeping!