6 Best Saltwater Fish For A 40 Gallon Breeder

A 40-gallon breeder aquarium is one of the more popular tanks used in the hobby.

They are often used for fish breeding purposes, coral frag tanks, shallow reef tanks, and more.  

It is a shorter and wider tank than others allowing for more flexibility with fish types, aquascaping, adding and removing fish, and creating an environment that is natural for breeding purposes is much easier with this tank. 

The dimensions of the 40-gallon breeder are 36” x 18” x 16”. 

The 40-gallon breeder tank is also great for use as a fish only, fish only with live rock (FOWLR), and full reef environments. 

They are easy to perform maintenance on and due to its unique dimensions, it opens the door for different types of fish that you are not able to keep in a regular-sized 40-gallon tank. 

When choosing fish for a 40-gallon breeder tank, consider the size of the fish when full-grown, other tankmates, and behavior patterns. 

This article will show you 6 of the best saltwater fish for a 40-gallon breeder tank. 

  1. Tomato Clownfish
  2. Bangaii Cardinalfish
  3. Cherub (Pygmy) Angelfish
  4. Six Line wrasse
  5. Carpenter’s Flasher wrasse
  6. Flame Hawkfish
best saltwater fish for 40 gallon breeder

1. Tomato Clownfish

Tomato Clownfish

There are many different types of clownfish that would be great in a 40-gallon breeder tank.

I chose the Tomato clownfish as my best choice as they are generally larger than other clownfish and very active.

Smaller clownfish like the Ocellarus can also be kept in smaller nano tanks where the Tomato clownfish can’t. 

They can grow to about 5” but it is more common for them to reach 3-4” which is a great size for the 40-gallon breeder.

The extra width of the tank will give them more swimming space.

Tomato clownfish are easy to care for and considered to be semi-aggressive. They are also safe to keep with corals.

They have a really nice orange and red body color with a white stripe.

They can add plenty of personality and color to your tank. 

2. Bangaii Cardinalfish

Bangaii Cardinal Fish (Pterapogon kauderni) isolated on white background.
Bangaii Cardinal Fish (Pterapogon kauderni) isolated on white background.

The Bangaii or Kaudern’s cardinalfish is one of the most unique saltwater fish to have.

They have a white/grey body color with white dots and black stripes which runs through the center of their eyes. 

The Bangaii will reach a maximum size of 3” and can be kept comfortably in a 40-gallon breeder tank. 

You can also keep them in a smaller tank like a 30 gallon if you wish.

They are a peaceful fish and will get along with most other tankmates. They are very easy to keep and will not bother your corals or invertebrates. 

These fish like to have plenty of live rock to swim around.

They are a slow-moving fish so ensure that they have hiding places and are kept with other non-aggressive fish.

Check out: 6 best saltwater fish for a 100-gallon tank

3. Cherub (Pygmy) Angelfish

The Pygmy (Cherub) angelfish is one of the smaller angels and will only grow to about 3” in size.

Many people will keep these fish in a 55-gallon tank, but with the extra width of the 40-gallon breeder tank, they can be kept without issues. 

These fish are very colorful fish and have a bright blue body with orange/yellow face. They require plenty of live rocks to graze on and hide in.

They will appreciate rock formations that create caves to hide in. 

The Cherub Angelfish can be kept with some corals and they are considered to be reef safe with caution. They may nip at LPS corals and clam mantles.

They are also aggressive towards other angelfish, especially their own breed. Only keep 1 male in the tank at the same time. 

Providing you keep your water parameters within the normal limits and perform regular maintenance, you should have no issues keeping these fish in a 40-gallon breeder aquarium.

4. Six line wrasse

Six line wrasse

Another great choice is the Six line wrasse. But there are a few considerations to watch out for with these fish.

First, you need to be aware that they are jumpers so it’s necessary to have a tightly fitted lid on the tank.

The Six line wrasse is also an aggressive fish with certain tankmates and you need to choose tankmates carefully. They like to pick fights with others. 

They will only grow to around 3” and are a fast-moving fish that likes to swim throughout all areas of the tank. They are quite energetic.

They are generally easy to care for and they don’t require perfect water conditions. They are great eaters and are not picky. 

These fish also require plenty of live rock in the tank. They will graze on rocks and use them to swim around and hide.

Providing you choose their tankmates wisely, you won’t have issues with the Six Line wrasse in a 40-gallon breeder tank.

5. Carpenters Flasher wrasse

Carpenters Flasher wrasse

Another wrasse that will make a great choice is the Carpenter’s Flasher wrasse. These fish will only grow to about 3” and the 40-gallon breeder is a great fit for them.

They are a very colorful fish that can be a showpiece fish in your tank. They are also very peaceful and won’t bother other tankmates. 

It is common for these fish to be bullied by other fish if they are aggressive. If possible, put the carpenter’s wrasse in the tank first.

The Flasher wrasse is easy to care for and is considered to be reef and invertebrate safe.

One concern with these fish is they are also a jumper so a tightly fitted lid is required to keep them. 

They are also an active swimmer and they don’t hide as often as other fish.

They are normally on full display to show off their beauty.

6. Flame hawkfish

Flame hawk fish hidden in a sps coral.
Flame hawk fish hidden in a sps coral. Neocirrhites armatus

The last fish on the list is the Flame hawkfish. These fish are a popular choice for many different tank sizes. They can be kept easily in a 40-gallon breeder tank. 

The Flame hawkfish are known for their personality and perching on branches of hard corals. 

They are very colorful with a bright red body and dark markings along the dorsal fins and eyes. 

They are easy to care for and are a peaceful fish but they should not be kept with small bottom dwellers.

Also, any inverts like snails and shrimp should be avoided. 

One unique trait of these fish is they tend to break up a fight between other fish. They act like a referee. Very interesting to watch.

They are reef safe and won’t bother with corals in your tank. If you have a 40-gallon breeder tank or plan on getting one, consider adding a Flame hawkfish to your list. 

How many fish can you keep in a 40-gallon breeder?

Depending on the size of the fish, you should plan to only keep 5 or 6 fish in a 40-gallon breeder aquarium.

An advantage that this tank has over others is the dimensions will allow for some larger fish that perhaps are not suitable for smaller tanks.


If you are looking to add fish into a 40-gallon breeder tank, any of the fish mentioned here are great choices. There are many more options available but these are just a few of the best choices.

Always research ahead of time and ensure that the fish you are planning to keep is going to be suitable for your tank for the short and long term.