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Can I keep Goldfish in 100 and 125 Gallon Ponds?

Can I keep Goldfish in 100 and 125 Gallon Ponds?

You're considering getting a goldfish, or perhaps you already have one (or two, or three). But how many goldfish can you keep in your pond?

The good news is, if you're keeping goldfish in a pond rather than in a tank, you could have a lot more freedom related to adding fish to a pond. Ponds come in all shapes and sizes, but even the most miniature ponds will measure at least 100 gallons. This article will examine how many goldfish you should keep in such small ponds, specifically 100-gallon and 125-gallon ponds.

Goldfish Are Some Of The Best-Known Pond Fish!

Lots of individuals falsely assume that goldfish ought to be kept in bowls. They imagine a goldfish swimming about in a little bowl of water on the coffee table, long fins trailing behind. While this may look impressive, it's a poor way to care for a goldfish. Goldfish bowls are one of the main reasons goldfish have such a bad reputation as a short-term pet.

Goldfish are hardy freshwater fish, making them ideal for pond fish. Since cold-water fish, they are capable of surviving waters a bit colder than tropical fish need. They are not too fussy and can be gulped with pellets or flakes.

The only problem with goldfish is that they grow up so much. They can grow up to 12 inches long; some have been known to develop up to 3 inches more. This makes a fish tank environment that is favorable to them. A 100-gallon fish tank is ideal for several goldfish to swim about and be content.

A few extra features for aquatic animals are more effective, such as a 125-gallon pond.

How Many Goldfish Can I Have In My 100 Or 125-Gallon Pond?

So, how many goldfish can you have in a 100- to 125-gallon pond? As with those in the world of aquariums and ponds, the answer depends on many factors. A typical pond stocking strategy is to add one common goldfish per 10 gallons of water. This means that in a 100-gallon pond, you could have 10 goldfish. And in a 125-gallon pond, you could have 12-13 goldfish.

Although goldfish are generally messier than other pond fish, you may want to decrease the density of your goldfish stocking slightly. A more conservative rule for stocking a goldfish pond is one fish per 20 gallons of water. This would translate to, for example, that you might keep five goldfish in a 100-gallon pond. You might then keep six or seven in a 125-gallon pond.

Of course, the more fish you have in your pond, the more filtration you'll need to keep the water clean. If you have a lot of fish in a small pond, you might need weekly water changes to keep the ammonia and nitrite levels in check. There s no specific guideline for how often you should do water changes, but a good approach is to change 10-20 percent of the water in the pond weekly.

What Affects The Number of Goldfish You Can Keep In A Pond?

We've touched upon a few aspects that will affect how many fish you can keep in your pond. These include total depth, filtration capacity, and water temperature.

Goldfish Size

A goldfish can grow quite large, so aim for a large enough pond to accommodate it if you intend to have that kind of fish. Also, you should know that goldfish are quite a bit messy, so having a pond that will need a lot of cleanup and maintenance will be a good idea.

While the 10-20 per fish rule we mentioned serves as an excellent general rule, some hobbyists prefer the gallons per inch approach. According to this rule, you should have at least 1 gallon of water available for every inch of fish in your pond. Both methods will yield a similar stocking density, but the latter requires that you appraise your fish and determine their average weight separately.

We recommend following the instructions on the mat of 10-20 gallons per fish, which is based on an adult goldfish's average size in inches. Afterward, even if your goldfish are small, they will quickly grow to full size.

Pond Setup

The specific type of pond you have will influence every aspect of stocking density. For example, if you have a lot of shaded submerged plants in your pond, they're an efficient means of cleansing the fish waste. This means you can increase your stocking density without worrying about the water quality declines.

In addition to sonic elements, decorative features can make your pond more densely populated. If you have a waterfall-type feature in your pond, the rushing water from the waterfall may help oxygenate the water and aid fish breathing. However, this may decrease the available area in your pond since fish will have to compete for space with the waterfall.

As a result, you may need to adjust the stocking density downward if you have this feature in your pond.


Other factors can be extremely important when it comes to stocking density, such as just how many fish you stock in your pond. If you're looking to install a pond with just goldfish, Give it a try! However, most people will opt for a combination of various kinds of fish. A common combination is a goldfish and koi because they're both members of the carp family.

We published an article on whether koi and goldfish should be handled together. We recommended that adult koi be kept apart from goldfish because their size difference renders the adult koi much superior to its juvenile counterpart.

However, you can maintain koi and goldfish together, but this usually involves juvenile koi being kept with adult goldfish. If you opt to have koi and goldfish in your pond, the stocking density is lower than if you were just maintaining goldfish.

Instead of maintaining 10 to 15 goldfish in a 100-125 gallon tank, you may find yourself with just 3 to 4 goldfish and 5 to 6 koi. This will depend on the tank size and the number of fish in it already.

Special Considerations For Goldfish Ponds

It hasn't escaped your attention by now that goldfish are high-maintenance pets. They produce a great deal of waste, are messy eaters, and need many places to swim. For this reason, goldfish ponds require a lot of setup and maintenance.

Pond Type

The number of goldfish you can keep in a preformed pond liner will depend on the dimensions of the water body. If you are using a small pond liner, you might be limited to keeping just a few goldfish. This is because preformed ponds are seldom deep enough for goldfish. An indoor pond, such as balcony ponds or those used as part of a water feature, will also require a more conservative stocking strategy.

If you have an outdoor pool at least 3 feet deep, you will need more space to work with. Swimming pools are sometimes home to a wide variety of fish, including goldfish, koi, and even pond snails. We often recommend a more significant, deeper pool for goldfish, as they will enjoy more swimming space.

If you have a pond of this size, you can keep 10-15 goldfish with no issue.

Pond Maintenance

Keeping a clean pond is critical for raising healthy goldfish, as these fish are messy and have many requirements. Filters are essential for goldfish ponds, as these appliances help to remove the waste the fish produce. Nothing will pollute a pond more rapidly than a couple of goldfish, and a spike in ammonia can kill your goldfish.

Pond filters explicitly designed for goldfish ponds are widely available on the market and should be chosen. The high-quality pond filter has considerable space for media, and it can adequately handle the heavy bioload generated by goldfish.

In addition to a filter, you will also need a pond pump and potentially a heater. Goldfish can't survive in warm-water ponds, but they can not withstand freezing temperatures either. Heaters warm your pond in winter and can help maintain a consistent pond water temperature all year.

Pond Depth

The final thing to consider is the depth level of your pool. In a previous paragraph, we explained that goldfish require quite a bit of swimming space. They spend a lot of time skimming along the surface, but they aren't water dwellers like catfish.

Goldfish like to have a body of water with lots of space to swim at all depths. A three feet deep body of water will satisfy the desires of goldfish and give these fish the cooler water temperatures they need. Having many small areas where the water is only several feet deep is also beneficial, as it can provide goldfish with a place to rest if required.

An average pool, which only measures between 100 and 125 gallons of water, will be between 2 and 4 feet deep. So, you should have no trouble accommodating a few goldfish in a swimming pool of this size.


Now that you know more about goldfish ponds, you can decide how many fish you want to keep in a 100 and 125-gallon pond. As a general rule, we recommend stocking your pond with no more than 10 fish for every 100 gallons of water. This will give your fish ample space to swim and keep them healthy for years to come!

Feel free to peruse our additional articles about how to care for your pet goldfish if you want to return to this information.

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