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How Big of a Tank do You Need For Angelfish?

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So many times, I’ve been asking myself how big of a tank should I get for my angelfish. Unlike guppies or tetras, angelfish usually require broader conditions to swim comfortably. Over the years, I’ve learned some helpful techniques to make sure you don’t overcrowd your tank. Using these, I was able to make my angelfish flourish.

The recommended tank size for angelfish is 22 gallons of water for an adult-sized angelfish. For every additional one, you’ll require 12 more gallons of water. From a different perspective, each inch of the adult angelfish length requires 24 square inches of an aquarium surface area.

In case it sounds complicated, I will go into the details of the calculating methods below. By using the techniques I’ve learned over the years, there is no doubt you’ll be able to grow your angelfish with great success. 

Finding The Right Tank Size For Angelfish

That might be the question every breeding novice asks. Once you have decided that you want to keep fish, you must identify and purchase a tank that will hold them. However, while some people obsess over the type of aquarium they need to buy, not to mention the price, others understand that the size matters even more. 

But how do you determine the right size for a tank to acquire? The answer to this question will determine the future of your fish, whether they thrive or if they ultimately meet a painful end.

Strangely enough, determining the right size for a tank isn’t that hard, not for angelfish. This is because aquarists have already reached a consensus with regards to the right tank size for angelfish.

But if you want to determine the volume on your own, there are three commonly utilized methods:

1 Inch For Every Gallon

This is the easiest method to understand.

Simply put, according to aquarists,[1] every gallon of water can support an angelfish 1 inch in length. As will be mentioned later on, the average size of an adult angelfish is 6 inches. But when it comes to calculating tank size, you need to consider the maximum size of the fish rather than the average.

In the case of angelfish, they can reach 12 inches in length. If each gallon of water can support 1 inch of an angelfish, then a proper adult angelfish requires 12 gallons of water. Now, as you’ll see below, it isn’t enough to simply consider the size of the fish.

Angelfish require plants, gravel, decorations, and the like, and all those objects will affect the available space in the tank. To avoid crowding, the general rule you should follow is to assign ten extra gallons to all those additional objects. 

In other words, one adult-sized angelfish will require 22 gallons of water. This is the tank size you need. If you add a second fish, that becomes 34 gallons. 

Four fish will require 58 gallons of water. If you can understand this equation, it won’t take you long to calculate the tank size you need regardless of the number of fish you want to keep. 

1 Inch For Two Gallons

This method doesn’t differ from the first one. Rather than assigning one gallon to every inch of fish, raise the figure to two gallons. The people who use this method argue that the ‘1 inch per gallon’ method ensures that your fish have the minimum amount of space they require.

In other words, they are merely making do with what you have given them. They are not necessarily enjoying themselves, and if you have multiple fish in a tank that was selected using the ‘1 inch per gallon’ rule, the chances of overstocking are quite high.

The ‘1 inch per two gallons’ rule ensures that your fish have ample space. You don’t have to assign the ten extra gallons to the plant life. The water quality is much higher because there is plenty of water to dilute any toxins or waste. As such, you don’t have to change the water frequently.

With this method, two adult angelfish will require 48 gallons of water. Neither approach is technically superior. Plenty of people have succeeded with the ‘1 inch per gallon’ rule. 

3. Surface Area (Most Recommended)

Many breeders disagree with the notion of using the length of the fish to determine the tank size. They argue that you cannot use the dimensions of the fish to determine the impact it will have on the tank. Even if all your angelfish grew to the same extent, some would be slimmer or plumper than others. 

To these breeders, while the ‘1 inch per gallon’ rule has a role to play, one must also consider the surface area of the tank because this measurement can more accurately determine the number of fish a tank can support. 

Fish might live underwater, but they breathe just like every other creature.

They need oxygen, and they generally pull it from the water. This oxygen comes from the world around the tank, and it enters the water through its surface. Not only do fish consume oxygen, but they release carbon dioxide. This also escapes the water through the surface.

This is why the surface area matters. The bigger the surface area, the higher the oxygen/carbon dioxide exchange, the more angelfish your tank can hold. You can have a container that has the right volume, but the surface area isn’t adequate for the number of fish you have. 

The fact that a tank can hold more water is irrelevant if it doesn’t have the right surface area. You are better off with an aquarium that can hold less water but offers a greater surface area. This is why the type of tank you choose is just as important as its size. Some aquariums provide a greater surface area than others. 

The consensus among breeders is that each inch of an adult fish requires 24 square inches of surface area.[2] If you are not sure how to calculate it, feel free to visit this calculator. This is the one I’ve been using as until now.

Does The Tank’s Size Matter to Angelfish?

Tank Size is an essential consideration because it can actually affect the health of your fish. People say that you should always get the most prominent tank possible. But the more significant the aquarium, the more money you have to spend to secure it. 

On the other hand, a small tank will cause overcrowding, which, in turn, will negatively impact the health of your fish. It will stunt their growth, reduce their lifespan, and incite violence.[3] So one cannot overstate the importance of locating a tank of the right size.

What Factors Impact The Ideal Angelfish Tank Size?

Every professional breeder you consult on the issue of tank size will ask you first to consider the type of fish you wish to keep. Different types of fish have different physical requirements and measurements, and that tends to affect the methods you use to calculate the tank size.

If you have set your sights on angelfish, then you have already won half the battle. This is because the requirements of angelfish are simple and straightforward:

Surface Area, Temperature & pH

Everyone knows that they are tropical fish. This will affect the surface area of water they require in a tank (you need 24 square inches of surface area for one inch of an adult fish. That figure jumps to 30 square inches for cold-water fish like goldfish). 

Everyone also knows that angelfish require a temperature ranging between 75 Degree and 84 Degrees Fahrenheit. Because they need slightly acidic water, you need to keep the pH between 6.0 and 7.5.[4]

Angelfish’ Average Size

Angelfish sizes do not vary that drastically. Adult angelfish in a tank typically reach 6 inches in length. Every so often, an angelfish will exceed that threshold, growing to 10 inches in length. 

Certain conditions will encourage angelfish to grow to larger sizes, such as large tanks and the right water conditions. In the wild, some angelfish can get as big as 12 inches. This is because they have access to natural food.

In fact, I’ve written an entire article on how to make angelfish grow faster and, in many cases, even larger. Remember, you must account for the size of the fish when calculating the tank size.

Decorations And Plants

You cannot keep angelfish in a bare tank. They need plants and decorations of one sort or another, either to breed within, swim through, or simply hide behind. However, most people who choose tank size using precise calculations do not consider the plant life and decorations. 

They do not realize that the figures they have calculated do not account for the amount of water these items will ultimately displace. But again, this is why you have to identify the type of fish you will keep.

Do that before selecting the tank size. If you know beforehand that you will keep angelfish, you can calculate the tank size by taking into account the water displaced by both the fish and the plant life. 

Fish Tank Companions

Adult angelfish can become territorial and aggressive, which is why they are seemingly content to live solitary lives. Young angelfish, on the other hand, tend to move in groups. 

Regardless of what your angelfish prefers, you can choose to add companions to its tank. But doing so will change the tank size you require. 

Understanding that an adult angelfish is perfectly okay on its own is helpful because it is quite easy to identify the right tank size for a single angelfish. Things only grow complicated when you add other fish to the equation.

How Many Angelfish Should You Keep in a Tank?

If you are not sure how many fish you should keep in your tank based on the surface area, the following equation should simplify things:

  • Assuming that you have a 35-gallon tank, start by measuring the length and width of the aquarium. Multiply the figures you get to acquire the surface area. 
  • Once you have the surface area, divide it by 12. This will give you the total inches of angelfish that your tank can hold.
  • Divide those inches by 12. This will give you the number of fish your tank can hold based on the surface area. Using this calculation, you will find that a 35-gallon aquarium can hold two fish. 

What is The Consensus on The Right Tank Size For Angelfish?

People have successfully used these estimates:[5]

  1. For nickel-sized fish, you should follow the ‘1 angelfish per gallon’ rule
  2. With quarter-sized fish, the ‘1 angelfish per 2 gallons’ rule will do
  3. Silver dollar sized angelfish require the ‘1 angelfish per 3 gallons’ rule.
  4. For pairing purposes, consider the fry and use the ‘1 angelfish per 5 gallons’ rule.

If you know the size of your fish, you just have to slot it into one of the categories above to determine the right tank size.

If you don’t have time for calculations and you just want a simple recommendation, this is what some breeders will say: you need at least 20 gallons for one fish. After that, you need ten more gallons for each additional fish.

What Types of Tanks Should I Consider For Angelfish?

If you are hunting for tanks, there are three types to consider:[6]

  • You have probably seen show tanks on TV. They are tall and narrow and, as you have probably noticed, they have a beautiful window that people can use to look at the fish. You can keep angelfish in show tanks, but they are best suited to small numbers. Their surface area is small. 
  • Long tanks are a little problematic because they require more room. They are also shallower, which makes them unsuitable for deep-bodied fish. But they have a decent display surface and impressive surface area.
  • Regular tanks come in many varieties. You have hexagonal tanks that have an attractive display but a smaller surface area. Round aquariums provide even less surface area, with the situation getting worse as the water level rises. 

If you are planning to buy a new fish tank, I highly recommend that you read my aquariums kits buyer’s guide before purchasing. I mentioned the one I’ve been using for years with great success. I also picked one kit which is suitable for experts (relatively large), after hours of research. It will surely save you money down the line.

Are Bigger Tanks Always Better For Angelfish?

Hobbyists always say that bigger tanks are still better for angelfish, and they are right. A broad tank gives your fish freedom. You are also less likely to observe aggressive behavior. Also, there is also less cramping. That means you don’t have to worry about the growth of your fish stunting. 

More to the point, large tanks are much easier to maintain because the water conditions remain stable for much longer. This is why you don’t have to change the water frequently. 

Even if dangerous elements like ammonia have invaded the water, it will take those elements much longer to achieve the levels of concentration required to cause harm in a large tank. If you don’t know what tank size to get, take the safe route, and buy the biggest one. You can’t go wrong with this choice. 

People think that it makes sense to buy a small tank when your fish are still young. They believe that they can simply upgrade to a larger tank down the line. However, this usually doesn’t happen.

This is because fish can’t speak. So they can’t complain. And if they mature in a small tank, they will learn to live with the discomfort. And because your angelfish seem okay, you will eventually choose to let them be. 

This is even though your angelfish are probably suffering considerable discomfort. You are also reducing their lifespan by confining them like this. You are better off getting the right tank size from the beginning. 


Angelfish require relatively large tanks. There is no way around this. The minimum size is 22 gallons. Therefore, raising angelfish could be expensive. However, if you already own a large aquarium, my guide above will make sure you don’t overcrowd it.

In case all you got is a small one, you may use my aquarium kits recommendations above to get started with a more advanced, fantastic adventure.