Best 40 Gallon Saltwater Fish

40 gallon saltwater fish tanks are one of the most popular and best sizes for an aquarium, they are not too big, nor are they too small, and can house plenty of wonderful fish.

Sure, you won't be able to have open water fish or fish that are too large in size, but there are many fantastic options that we will be looking at.

40 gallon saltwater fish

Regardless of not being huge in size, with a 40 gallon (151 liters) aquarium you can comfortably create an awesome reef tank with a nice variety of saltwater fish that we'll be discussing here.

If you would rather watch my video on the best saltwater fish for a 40 gallon aquarium, you can do so below:

Common 40 Gallon Tank Dimensions

Typically, most 40 gallon (151 liters) tanks come in the same, or similar dimensions, but there are some unique exceptions.

A 40-gallon "breeder tank" is a wide tank, usually measuring 36 inches (91 cm) in length x 18 inches (45 cm) wide x 16 inches (40 cm) deep.

They are 6 inches both longer and wider than the 20-gallon long tank, and roughly the same height as a standard 10 or 20-gallon long aquarium.

The tank is perfectly sized for fish, giving them plenty of swimming room and space, which is great for establishing territories.

Long tank dimensions

A 40-gallon "long tank" is a tall tank that will be 48 inches (122 cm) in length x 12 inches (30 cm) wide x 16 inches (40 cm) deep.

So, when compared with the 20-gallon long aquarium, the length is the same as well as the width, however, there are 6 inches of extra depth.

The amount of water both hold as well as their unique and user-friendly shapes are fantastic for creating a healthy saltwater aquarium environment. The filled weight of a 40 gallon aquarium is approximately 455 lbs (206 kg) and when empty, the weight is typically 55 lbs (25 kg).

The Best 40 Gallon Saltwater Fish Tank

Below is the best 40 gallon fish tank currently on the market - perfect for keeping a thriving community of saltwater fish for a 40 gallon tank:

  • This 40 gallon (151.4 liter) aquarium is the perfect home for the fish mentioned on our list below. It is acrylic rather than glass, which is often the preferred choice, especially for less experienced hobbyists.
  • The dimensions are 36 inches x 15 inches x 16 inches (91.44 cm x 38.1 cm x 40.62 cm) which are compatible with most home spaces.
  • It is a combo set, which includes the tank, reflector, and a 24 inch (60.96 cm) electrical light fixture.
  • The acrylic screen is clearer than glass and 17 times stronger as well as being only half the weight!
  • Super safe around both children and pets.
  • An incredibly modern and slick design that will show off the beautiful saltwater fish perfectly.

Choosing the Best Saltwater Fish for a 40 Gallon Tank

When it comes to selecting the best saltwater fish that are well-suited to a 40 gallon (151 liters) aquarium, there are certain criteria that should be adhered to for you to ensure a stress-free and enjoyable time with your saltwater community.

It is key to note that if you have found fish that are suitable for a 20-gallon saltwater tank, or less, they will be more than appropriate for a 40 gallon (151 liters), and you can actually add more to fill up the extra space.

Here are the criteria to be aware of before stocking your 40-gallon tank with saltwater fish:

  • They should be peaceful, community fish, that play well with others.
  • Small to medium-sized fish, 5 to 6 inches (13 cm to 15 cm) in length maximum.
  • Hardy fish that are not prone to common saltwater fish diseases.
  • Brightly colored fish - your tropical fish tank should be brimming with awesome and unique colors.

Top 40 Gallon Aquarium Saltwater Fish

Out of all the fish listed below, you can add between 8 to 16 of in total to your 40 gallon (151 liters) aquarium. There is a short description of each fish, and it is then your decision as to which ones are best suited to you, your tank, and their potential tank mates!

It won't be long until your tank is displaying some incredible colors to match a busy and active community. If you have plenty of coral you wish to stock in your tank, you shouldn't add as many fish due to the water requiring more maintenance.

Something else to note is that 40 gallon (151 liters) fish tanks can hold even the larger clownfish species.

The video above was created by us here at Lionfish Lair, we chose our favorite three fish from the list, but keep reading as there are many, many more for you to check out! Enjoy the list.

List of the Top 10 Fish Types for a 40 Gallon Aquarium

1. Blenny

Although, you should only populate your tank with one individual Blenny, the Tailspot, Two Spot, Fangtooth, Midas, Canary, and Harptail are all great and beautiful options.

2. Cardinalfish

The Banggai, Yellow, Pajama, or Longfin Cardinalfish are all fantastic choices, but you should only keep one of these in your 40 gallon tank.

3. Cleaner Goby

These guys are not only beautiful, but they are extremely helpful too. Neon, Yellow Line, Shark Nose, or Hybrid gobies are the best options, and you can even keep them in pairs.

4. Clownfish

Due to the size of the aquarium, you can keep any clownfish species and they will be fine. It is recommended to keep between 5 and 6 of the smaller species (Ocellaris or Percula), and 1 or 2 of the larger species (Tomato or Maroon).

5. Damselfish

Damselfish come in many different colorations, shapes, and sizes, but one thing remains the same - they are all truly stunning fish. The three most suited to a 40-gallon tank are the Azure, Blue, and Blue Devil Damselfish, but make sure to keep them individually.

6. Dottyback

Orchid and Neon Dottybacks are great choices. However, you should stay away from the other species of Dottyback, and also only keep one of the same species.

7. Fairy Basslet

Both the Royal Gramma and the Blackcap (also known as a fairy basslet) will suit a 40-gallon saltwater aquarium perfectly. Make sure to keep only one Fairy Basslet as they have been known to not play well with their own kind.

8. Fancy Goby

Fancy gobies are one of the most unique-looking saltwater fish in the hobby. Typically displaying unique patterns and bright colors, the Clown, Two Spot, Yasha, and Court Jester gobies are the best options. You can only keep one fancy goby per 40 gallon tank.

9. Hawkfish

Despite looking somewhat menacing, hawkfish are some of the friendliest and also awesome-looking fish you are likely to come across. Flame, Longnose, and Falco Hawkfish are the best choices, but make sure to keep only one.

10. Jawfish

Jawfish are great if you have deeper sand or substrate than most 40-gallon tanks. Having one or two Yellow Head or Blue Spot Jawfish will provide much entertainment as well as brighten the place up.

All of these fish are perfect for a 40 gallon (151 liters) saltwater aquarium, and they are compatible with low-experienced hobbyists too. In addition to fish, you can start to look at adding invertebrates such as sexy shrimp, and more!

Required Equipment for a 40 Gallon Aquarium

It is equally, if not more important to gather the right equipment for your 40 (151 liters) gallon tank than it is to fill it with saltwater fish.

So, below is a list of all the equipment you will need for your 40 gallon (151 liters) saltwater aquarium:

  • A lid or a mesh net to stop your fish from jumping out of the tank. Sure, you may think that you don't need it for whatever reason, but unfortunately, there are too many fish casualties as a result, and it is better to be safe than sorry!
  • An air pump and airline tubing, or even a powerhead pump to increase/regulate the water flow in your 40 gallon tank.
  • A sponge, canister, or live rock will help with filtration.
  • You will need a 200-watt heater.
  • An LED light such as a blue filter light is a good choice as it can help mimic the moonlight your fish would typically see in the wild.

Guys, if a 65-gallon saltwater fish tank is a good size for you and your fishkeeping ambitions or requirements then don't sweat it! We have created lists for many different sized aquariums:

10 gallon saltwater fish

20 gallon saltwater fish

30 gallon saltwater fish

55 gallon saltwater fish

65 gallon saltwater fish

75 gallon saltwater fish

90 gallon saltwater fish


A 40-gallon saltwater fish tank is a great option for whatever level hobbyist you are. Fortunately, due to being a great size, there are many awesome and colorful fish that you can choose to populate your 40 gallon (151 liters) fish aquarium. Just make sure that you do not overpopulate your tank as the health and happiness of your fish should be the number one priority.

One final consideration is to make sure you have enough space in your home or apartment for your 40 gallon (151 liters) tank. While the tank dimensionally is not huge, you need space in the right places in your home or apartment to fit it in appropriately where it suits both you and your fish.