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How Big Do Black Moor Goldfish Get?

Renee Whitmore
Last Updated on
by Renee Whitmore

Going to the pet store to pick out a fish is an exciting time, and the black moor goldfish may understandably catch your eye.

But as you drive home with your black moor, you might start reconsidering the tank you purchased; unlike puppies and kittens, it can be difficult to tell if you have a young or adult fish on your hands.

Fear not, for we’ll share everything you need to know about the black moor goldfish size so you can be a prepared fish owner.

How Big Does a Black Moor Goldfish Get?

Black Moor Goldfish

If your first impression of a black moor is that it’s cute and tiny, then you’re likely looking at a growing goldfish because black moors average six to eight inches long.

That said, if you give your black moor quality food, it could grow larger than eight inches.

You’ve likely heard the saying that a fish will grow to the size of its tank. That’s a myth that probably came from fish owners having fish with stunted growth. Therefore, you can put your black moor goldfish in a large tank without worrying about it growing to an unmanageable size.

Other Features of a Black Moor Goldfish

Aside from its length, the chubby, egg-like girth is iconic to the black moor goldfish. They have long, flowing fins, so you must keep their tank free of any sharp fish toys and plants that their fins could get caught in.

The black moor also has protruding eyes, and scientists discovered that these goldfish have myopic eyesight, meaning they don’t see well.

Between the black moor’s round shape and its poor eyesight, they’re a sluggish moving fish. Therefore, it’s crucial to give them plenty of space in their tank.

Ideal Tank Size for Black Moor Goldfish

At a very minimum, you should provide one black moor fish with a 20-gallon tank. However, it’s best to give him 30 gallons. For every additional black moor that you add to the tank, you’ll need to factor in an extra 10 gallons.

Of course, if you end up including different fish species in a black moor’s tank, then you’ll need to add the appropriate number of gallons to match the fish species’ size.

When in doubt, though, more space is always better; black moors are generally friendly fish, but they enjoy having space to themselves. Therefore, if you pack too many fish into your black moor’s tank, he’ll likely feel stressed and may even become aggressive.

Setting Up Your Tank For Your Black Moor’s Size

Because the black moor goldfish size is bulkier than many other species of goldfish, it’s essential to consider its tank set up to ensure your black moor is comfortable.

Below are some recommendations for how to keep your black moor happy in its tank:

  • Choose a tank that’s longer than it is tall
  • Don’t fill up the tank with too many plants and toys
  • For the plants and toys you do have, place them at the back of the tank

The reason for the recommendations above is that black moors aren’t great swimmers because of their round size and poor eyesight.

So, by having a short but long tank, your black moor won’t have to swim as much to reach the surface to eat its food flakes. Similarly, keeping plants and tank toys in moderation and towards the back of the aquarium will give your black moor plenty of space to swim in open water.

Determining How Much to Feed Your Black Moor Goldfish

Whether you own a growing black moor goldfish or your fish is already an adult, but you fear you’re not feeding him enough or too much, this section will help clear up your doubts.

It’s essential to feed your black moor according to its size. As a general rule, a fish’s stomach is as big as its eye. So, since black moors have large, bulging eyes, this means they may need more food than other fish in your tank.

Nevertheless, most fish owners tend to overfeed their fish.

If you’re struggling to “eyeball” how much you should feed your black moor, another trick is to use the two-to-three-minute rule: Put a small number of goldfish flakes (or whatever high-quality food you provide your fish) into your black moor’s tank. Let your fish eat those flakes and add a little more if he does.

Continue this step for two to three minutes. After the two or three-minute mark, you can be sure that your fish had enough to eat (even if he acts like he wants to eat more).

Not only is it essential to feed your black moor an appropriate amount of food for its size to prevent it from having health issues, but it also helps keep the water clean. If there’s too much leftover food in the water, it can raise ammonia levels, which can wreak havoc on your black moor’s health.

More on Feeding Goldfish:

What Is the Biggest Goldfish on Record?

Black Moor Goldfish size

There doesn’t appear to be data on the biggest black moor goldfish. However, according to the Guinness World Records, the biggest fish within the goldfish species measured 18.7 inches.

The winner of this title came from a goldfish owner in the Netherlands back in 2003.

Since black moor goldfish typically average up to eight inches, it’s unlikely your fish will come close to beating this record. However, if your fish somehow inherits a giant growth gene, now you know the benchmark it would have to reach to break the world record.


The black moor goldfish size is a delight for fish owners—they have an adorable round profile and charming buggy eyes.

To ensure your black moor has a happy life in its tank, he must have dozens of gallons of water to swim around in.

Furthermore, you should keep plants trimmed and tank toys in a designated area. That way, given a black moor’s poor eyesight and large size, it will have enough space to swim around.

About Renee Whitmore
Renee Whitmore
Renee Whitmore is an American college professor and freelance writer from North Carolina. She holds a Bachelor’s Degree in English and a Master’s Degree in English Education. When she is not driving her teenage son to wrestling practice or learning the ins and outs of Fortnite from her younger son, she is working on her first book to be published soon.
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