Best 125 Gallon Aquarium

Last Updated on 2023-08-08

Buying a 125-gallon fish tank can be difficult especially if you have little experience with aquariums. The buying process involves plenty of thought and consideration to pick the best 125-gallon aquarium that offers everything you need and is within your budget.

According to us, the best 125-gallon aquarium is the SC Aquariums 120 Gallon Starfire Glass Aquarium. It has excellent build quality, comes with a built-in overflow box, and overall offers great value for the money.

Read on to learn more about the best 125-gallon aquarium you can buy. Also discover tips on buying, setting up, and maintaining a 125-gallon aquarium. Happy reading!

125 Gallon Aquarium Buying Guide

Here are some factors to consider when buying a 125-gallon aquarium.

1. Is It the Correct Size?

Before buying a 125-gallon aquarium, you need to decide whether it is the correct size for you. Aquarium sizes are chosen depending on the number and species of fish, available space, and other considerations. A 125-gallon tank is certainly not a small one and maybe too big for you if you plan on having a small number of fish in it. Standard aquarium sizes start from 15 gallons and can go up to 220 gallons or even more than that. 

Check out this guide for more details on aquarium sizes. In most cases, the bigger your aquarium is, the better it is for the fish and aquatic plants.

2. Price

The price of an aquarium should be an important consideration when buying one. It should fit your budget and leave you with enough money to buy other aquarium equipment and accessories. The rule is simple – the larger the aquarium, the higher its price. On average, a 125-gallon fish tank can set you back about $ 700. Moreover, some fish tanks come with additional features such as a stand, LED lights, cover, filter, etc. The more equipment and accessories a fish tank comes with, the higher its price tag will be.

3. Where to Place It

Deciding where to place a 125-gallon is important. When it comes to big aquariums, a big problem for owners is making space for them. Due to its large size, it can be difficult to allocate space for a big fish tank, especially in apartments or small houses. So, before you purchase a 125-gallon aquarium, make sure you have adequate space to accommodate it.

4. Size and Species of Fish

The size and species of fish you have and will have (in the future) is a key consideration that should go into determining the best size of an aquarium for you. Species that don’t grow up to become too large, such as bettas, are ideal for small aquariums. Larger species, such as angelfish, need more room to grow and move around. A 125-gallon tank is easily large enough to accommodate most large species. 

In addition, the number of fish you plan on introducing to your aquarium is another thing you must consider.

5. Aquarium Material: Acrylic vs. Glass

Aquariums are usually made of glass or acrylic. For a 125-gallon fish tank, glass is the better material for a number of reasons. Glass aquariums are cheaper and more resistant to scratches compared to acrylic ones. Scratches from rocks and pebbles can easily appear at the bottom of acrylic fish tanks. To its credit, acrylic is easy to repair than glass. However, between the two materials, glass is the better and more cost-efficient choice for 125-gallon aquariums.

The Best 125 Gallon Aquarium

Aquariums come in many different sizes and varieties. A 125-gallon aquarium is a popular size in the large aquariums category and choosing one from a reliable manufacturer is important. Here, we’ve picked the best 125-gallon aquarium for you – the SC Aquariums 120 Gallon Starfire Glass Aquarium. While it is 5 gallons short of having a 125-gallon capacity, we think it is the best option in this size category.

Why this particular aquarium, you might ask? We’ve chosen this aquarium based on extensive personal experience and testing and found it to be the best choice among other similar options. All of our reviews and opinions are based on in-depth personal experience, so you can rest assured that you’re getting authentic advice.

SC Aquariums 120 Gallon Starfire Glass Aquarium – Our Top Choice

Product Highlights 

The rectangular 120-gallon Starfire Glass Aquarium is manufactured by SC Aquariums and is in our opinion, the best aquarium in its category. It has euro-bracings, a built-in overflow box, and is made of Starfire glass. Available at around $ 1,495 on Amazon, it isn’t one of the cheapest options available, but provides excellent value for the money and has great build quality.


  • Made from 12mm thick Starfire glass (glass that has low iron content)
  • Has a built-in overflow box
  • Dimensions (L x W x H): 48 x 24 x 24 inches
  • Comes with an SCH40 plumbing kit

What We Like About The Starfire Glass Aquarium 

For its $ 1,495 price tag, the SC Aquariums 120 Gallon Starfire Glass Aquarium has much to offer. We love the build quality of the aquarium and the fact that it is euro-braced. The glass used is Starfire glass, which has low iron content. This means the glass won’t have the bluish-green tint you normally see. Moreover, the glass is smooth and clear and the silicone joints at the bottom are great. The aquarium also has a removable black background. 

What We Don’t Like About The Starfire Glass Aquarium

While there’s much we appreciate about this 120-gallon Starfire Glass Aquarium, there are a few things we aren’t exactly enthusiastic about. One of them is its price tag. While large aquariums aren’t exactly cheap, you can find other 120-gallon aquariums at lower prices. Furthermore, the aquarium doesn’t come with a stand, which we think should’ve been included. 

Great build qualityPrice is relatively high
Built-in overflow boxDoesn’t come with a stand
Comes with an SCH40 plumbing kit 
Beautiful and clear Starfire glass 
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How To Set Up A 125 Gallon Tank

Setting up a 125-gallon tank for the first time can be a difficult task, especially if you don’t have any prior experience. Here, we’ve listed down some important tips and guidelines to help you get started.

1. Assemble the Fish Tank and Place It in a Suitable Spot

The first step to do when setting up your tank is to assemble it and place it in a suitable spot. The place should have access to sunlight or artificial light. The tank should also be kept away from harmful chemicals (such as insect sprays or air fresheners).

To set up your aquarium, build its stand (if it has one), install the background, and plug in the lights and other equipment.

2. Wash All Ornaments and Gravel Thoroughly

Before putting any ornaments, decorative pieces, and gravel into the aquarium, you need to thoroughly rinse them with hot water to remove any dust, dirt, or paint. Make sure the decorative pieces aren’t those that will release harmful chemicals into the water.

Once the ornaments are washed, put them on the bottom of the tank and add gravel slowly and gently to avoid scratching the bottom.

3. Fill up the Tank With Water

The next part is the fun part. Fill up your tank with water using a hose. The water should be filled slowly as doing it too fast will turn it cloudy after coming in contact with the gravel.

Here’s another important thing you need to keep in mind. Make sure the source of water you’re using is clean and free of any harmful chemicals. While tap water in the US is generally fine, bad tap water can cause a host of different problems.

4. Connect and Turn on the Equipment

Once the tank is filled with water, you need to turn on the filter, heater, and other equipment. You can also turn on the lights. Also note that turning on the electrical equipment after the tank has been filled is important. Doing it before might damage the equipment.

In addition, remember to keep your lights on for only 8 to 9 hours a day. Keeping them on for longer can promote algae growth which can lead to other problems. 

5. Let the Aquarium “Cycle”

Cycling refers to the process of the establishment of a culture of beneficial bacteria that carry out various biological processes to keep the water quality at optimum levels. These bacteria live on the substrate, the filter media, and other surfaces in your tank. Simply put, cycling is an essential part of setting up your aquarium and may take anywhere from a couple of weeks to a month to establish.

6. Check Water Conditions Frequently

During the initial days and weeks of setting up your aquarium, frequently testing and monitoring water conditions is of paramount importance. This testing is done to ensure that the cycling process is going smoothly and that the bacterial colonies are being established in the tank. Testing is also done to monitor the water quality and pH.

All of this is necessary to ensure your aquarium is fully ready to accommodate fish when they’re introduced.

How To Maintain A 125 Gallon Fish Tank

So, you’ve set up your new 125-gallon aquarium and everything’s working fine. But what next? How should you clean and maintain your fish tank and how often should you do that? Below we’ve collected some tips to help you with aquarium maintenance.

1. Regularly Test the Water (Temperature, pH, Etc.)

Testing the water regularly is one of the most important parts of regular maintenance. Many beginners often make the mistake of not testing water parameters regularly once the aquarium has been set up.

But water conditions don’t remain constant over time. They can change and be influenced by several factors. Therefore, it is important to frequently test the water quality, pH, and temperature as part of your maintenance routine.

2. Clean the Tank and Other Equipment

Cleaning your tank and its equipment is a simple yet effective part of maintenance that can prevent many of the problems that commonly affect aquariums. Skipping cleaning is something you should never do.

Cleaning the tank involves cleaning the inner walls of the aquarium, removing algae on the walls using an algae scraper, and cleaning or changing the filter media.

3. Avoid Overfeeding Fish and Overcrowding Your Tank

Overfeeding fish and overcrowding the tank are two common mistakes inexperienced individuals make. Overfeeding refers to putting more fish food in the aquarium than your fish need. The rest of the uneaten food remains in the water and turns toxic, affecting its parameters. To avoid this, simply give your fish enough food that they can eat within a few minutes.

Overcrowding means stuffing your tank with large numbers of fish. This can create a plethora of problems especially if your tank wasn’t meant to accommodate so many fish. Only introduce as many fish as your aquarium can accommodate to prevent this.

4. Remove Fish Waste and Plant Debris

Removing fish waste, plant debris, and other pollutants from the water should be a key part of the regular maintenance routine of your aquarium. Like all living creatures, fish produce waste and if that waste remains in the water for extended periods, it can start affecting the water quality. 

5. Change the Water Regularly

In case you didn’t know, your fish tank’s water needs to be changed on a regular basis. This should be done even if your water looks clean and clear to you. The water needs to be changed due to several reasons. 

Firstly, the minerals and nutrients present in water essential to the fish and plants can get depleted over time and need to be replaced. Secondly, fish waste and other pollutants absorbed in the water can negatively impact the health of the fish.

We recommend changing your aquarium’s water every week or once every two weeks. During every change, you need to replace 10 to 20 percent of the water.

How Many Fish Can Be In A 125 Gallon Tank?

Here’s a question you might be wondering about: exactly how many fish can a 125-gallon fish tank accommodate? The answer to this isn’t as simple as you might be expecting. The number of fish a tank can accommodate depends on the average size of the fish. 

If you have smaller fish (about 2 to 3 inches in size), you can fit about 80 to 100 of them. But if you’re keeping larger species such as the angelfish, then you’d only be able to fit up to 15 – 20 of them. Since it’s highly unlikely you’ll be keeping fish of a single species or size, consulting your local fish store or pet shop is a good idea to work out a combination of species best suited to a 125-gallon tank.


Here, we’ve answered other related questions you might have about 125-gallon aquariums.

How Much Does A 125 Gallon Fish Tank Cost?

The price of a 125-gallon fish tank can vary greatly depending on the brand, build quality, features, included equipment, and other factors. On average, the price of a good quality 125-gallon aquarium is about $ 700.

How Much Does A 125 Gallon Aquarium Weigh?

125-gallon fish tanks are large aquariums and quite heavy. On average, a 125-gallon tank weighs over 200 pounds (91 kg) when empty and around 1400 pounds (636 kg) when filled with water. To support such a large weight, the aquarium’s stand or support needs to be very sturdy and strong.

Will My Floor Hold A 125 Gallon Aquarium?

If you’re worried about the ability of your floor to support a 125-gallon aquarium, you’re not alone. Many people get worried and have second thoughts when they get to know how much a 125-gallon fish tank weighs. But you needn’t worry as most residential floors can easily support it. However, the tank should be on a sturdy stand.

What Size Heater For A 125 Gallon Fish Tank

For a 125-gallon tank, you need a heater that has a heating capacity of between 350 and 400 watts. Smaller aquariums will require substantially less heating power.

Final Thoughts

125-gallon aquariums belong to the large category of aquariums and can cost about $ 700 on average. If you want to buy a 125-gallon aquarium, there are many factors that you should consider such as your budget and the size and species of the fish you plan on keeping. According to us, the best 125-gallon aquarium you can buy is the SC Aquariums 120 Gallon Starfire Glass Aquarium as it offers excellent value for the money.

In this guide, we went over everything you need to know about buying, setting up, and maintaining a 125-gallon aquarium. Thank you for reading and we hope you enjoyed it!

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