How Many Goldfish in 55-gallon Tank?


There’s a lot of misinformation about tank size requirements for the popular Goldfish simply because many people who aren’t in the hobby are the ones giving them out. Let’s correct that today by giving you tried and tested tips and suggestions.

How Many Fish Can I Have In A 55-Gallon Tank?

Let’s start with a 55-gallon tank, a size reasonable enough for Goldfish.

The tank size requirements of Goldfish depend on several factors, including the species. Common Goldfish are bigger than Fancy Goldfish, so you can have at most a pair of them (Common) in a 55-gallon tank.

Common Goldfish are the red, yellow, and white ones you find at carnivals and county fairs. Examples of these and those that grow to a foot long are Comets, Shubunkins, Nymphs, and Watonais.

What Size Tank Do I Need For 4 Fancy Goldfish?

Fancy Goldfish are those with fat bodies and double tails.

A group of 3 to 4 Fancy Goldfish could fit a 55-gallon tank.

Examples of Fancy Goldfish are Fantails, Celestials, Bubble Eyes, Veiltails, Lionheads, Moors, and Pearlscales.

Now before you start to argue about these tank sizes, let’s present our justifications for our answers.

Reason #1: The size of the fish

If you’ve been encouraged to keep a 10, 20, or 30-gallon setup for a group of Goldfish, please research first the maximum size a Goldfish grows into. This small tank setup is a temporary one for a small Goldfish at best, while it is still about 3 inches long. Soon, you’ll have to look for a bigger aquarium as your fish grows, and you’ll end up upgrading from tank to tank and spending more in the long run.

One thing that a lot of newcomers to the hobby don’t realize is how big these fish get. Common Goldfish can grow up to 14 or even 16 inches in length, 12 inches being the average adult size.

On the other hand, Fancy Goldfish can grow up to 8 inches long, the average being 6 inches.

How Many Goldfish in 55-gallon Tank?
How Many Goldfish in 55-gallon Tank?

You need a bigger tank so that big Goldfish can swim comfortably in it. While it is indirectly true that small tanks limit how big your Goldfish will grow, it is unnatural and unnecessary to keep them from reaching their full potential.

In a crowded space (especially with poorly maintained water), Goldfish release hormones in the water that limit their growth. But this could lead not just to stunted growth but deformities as well. Their lifespans also shorten.

If given ample space and proper water maintenance, the Common Goldfish (such as those in a pond) will grow up to 12 or even 14 inches upon maturity. They will also live 10, 15, or even 20 years.

Reason #2: The way they swim

Unlike some other fish that dart straight, Goldfish flex their bodies back and forth to get from one place to another. That’s why we advise that the tank you get for these fish not just be wide but also tall. This gives them enough room to wiggle around comfortably without bumping into objects or the walls of the tank.

Some Goldfish varieties, especially, have naturally protruding eyes and must be kept safe from obstacles that can hurt them. Putting them in a small space would make it harder to avoid obstacles.

Reason #3: Comfort in pairs

Another thing to remember when taking care of Goldfish is to keep them in pairs. It’s not an absolute must, but they’re happier that way. So that extra fish must be taken into account when thinking of tank sizes.

Reason #4: Their bioload

Even though some people like to overstock, remember that it’s harder to keep the water clean when there’s too much fish inside, more so with how messy Goldfish are.

This amount of waste that they produce is one of the biggest challenges with keeping Goldfish. Having a smaller tank will require you to clean and do more water changes often. Otherwise, all that waste in the water will poison your fish slowly.

Here is where effective filtration comes in. The key to success for overstocking is keeping those toxins low to non-existent. When we say toxins, we mean ammonia, nitrites, and nitrates that fish produce from their waste. This is bioload.

As long as all that bioload can be cleaned out and processed by your filter, your Goldfish will survive even in a smaller space (but not too small!). So there exists that balance between tank size and how effective your filtration system is.

Reason #5: Other items in the tank

Are you going to keep a tank with just fish in it? We didn’t think so.

You’ll have to consider the bare essentials: a powerful filter (or two) to keep the water clean, a thermometer to monitor the temperature, and a heater if you’re keeping Fancy Goldfish.

Of course, you’ll be thinking of a proper setup for your Goldfish so you’ll put in these items as well:

  • Substrate – some Goldfish-keepers prefer not to put substrate for easier cleaning, but most like to place gravel or sand
  • Decorations – Goldfish love to hide and entertain themselves, thus the need for decorations. Make sure these have aquarium-safe paint and are clean.
  • Live or fake plants – having plants mimic the natural habitat of fish in the wild, lessening the stress levels of your pets. Less stress means healthier fish.
  • An air pump/bubbler – Goldfish need lots of oxygenation but be careful as younger and slow-moving Fancy Goldfish will not appreciate high-velocity air streams. Stronger swimmers won’t have a problem.

All these items take up space in your tank, too.

So you see it’s not just a matter of putting as much fish as you can in a certain tank size.

What Size Tank Do I Need For 6 Goldfish?

If you endeavor a more delightful tank with lots of Goldfish, it’s possible with the right-sized aquarium.

What size tank do I need for 6 Goldfish?
What size tank do I need for 6 Goldfish?

6 or 7 Common Goldfish can fit in a 125-gallon tank. If you have a pond to put these Goldfish in, it would be for the best. If you’re taking care of Fancy Goldfish, 6 of them can live comfortably in a 75-gallon minimum.

Those sizes are enough to give you a more relaxed maintenance routine and also give your Goldfish a more relaxed, spacious atmosphere even as they grow to their full size. Of course, never forget how big a part filtration plays in any setup.

Ponds are the best homes for Goldfish since they can roam around freely and live in a natural environment.

Accepting Exceptions

We at Explore Fish World understand that some people have been keeping Goldfish for years in overstocked aquariums and being successful at it. We commend those people who keep their pets healthy and know what they’re doing. As we said, that setup is a lot harder to maintain and hardly fit for the newbie.

On the other hand, some people find it hard to keep nitrates low enough even in a 75-gallon tank with only a few Goldfish. Again, we point not just to the size of the tank but the effectiveness of your filtration system.

Whichever you choose, always put the welfare of your pet first. Your Goldfish is depending on you to provide what’s best for it.

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