5 Best Fish Tank Ideas for a 40-Gallon Breeder Aquarium

The 40-gallon breeder aquarium is a very popular size because of its 36″ length x 18″ width x 16″ height (91 x 46 x 41 cm) dimensions. Other 40-gallon tanks have a more rectangular base, but the 40-gallon breeder tank has a deeper base without being too tall so that you can easily reach inside to clean the aquarium and catch fish that you have bred. The 18-inch width also lets bigger fish to turn around more easily, making this one of the first footprints that allows you to keep either a larger solo specimen or community of fish. Keep reading to learn about our top 5 fish stocking ideas for a 40-gallon breeder tank.

1. The Flowerhorn Tank

Flowerhorn cichlid

This hybrid New World cichlid is known for having jaw-dropping, colorful patterns and a large nuchal hump that grows on the heads of males. Flower horn fish are especially valued in certain Asian cultures because they are thought to bring good luck and prosperity. While flowerhorns are quite playful and personable towards their human owners, they can be fairly aggressive toward other smaller animals in their territory. We suggest keeping one in a 40-gallon aquarium with no other tankmates. When it gets bigger, your wet pet will eat lots of food and therefore need more water changes to keep the water clean. After many years of enjoyment with the 40-gallon fish tank, we recommend upgrading to a 55 or 75 gallon aquarium for your growing pet.

2. The Community Aquarium

Bolivian rams, julii corys, and black skirt phantoms

If one showpiece fish per tank is not your idea of fun, let’s go the opposite direction and fill the 40-gallon tank with many different species. First, we will be getting one to three pairs Bolivian Rams (Mikrogeophagus Altispinosus). They are known for their beautiful, trailing fins and will serve as the 3-inch (7.6 cm) centerpiece fish for this community tank. Make sure you have plenty of decorations and aquarium plants to obscure line of sight to avoid territorial disputes. Then add a school of julii corydoras that will help clean the fish tank by constantly scavenging for leftover food stuck in the substrate. Since you have a medium-sized aquarium to work with, choose a stockier, midlevel schooling fish. We like black phantom tetras (Hyphessobrycon megalopterus) because of their strikingly high dorsal fins.

All of these fish are pretty hardy, live in similar water parameters, and are safe with aquatic plants. These fish eat omnivore food, including frozen bloodworms, pellets and Repashy gel foods. This is the foundation of your 40-gallon community tanks. Feel free to spice it up with some of your personal favorites – like a rare pleco, snails, rainbow shark, or some oddball fish.

3. The “Breeding for profit” Tank

Female albino long fin bristlenose pleco

You can spawn many species with a 40-gallon aquarium. This catfish runs between 4-5 inches (10-13 cm) long but has giant finnage that takes up more space than normal bristlenose plecos. They also require bigger caves to accommodate their wider wingspan. You can breed them in a smaller aquarium, but once they start producing lots of fry, you will have to regularly move the offspring to other fish tanks.

For filtration, we like to use gentle sponge filters to keep the babies from being sucked up by accident. We then prepare the adults for breeding by giving them plenty of their favorite foods like Repashy gel food and sinking wafers. Fry have smaller mouths than adults and love to eat driftwood, baby brine shrimp, crushed flakes and canned green beans.

There are many types of long fin bristlenose plecos, including super red, green dragon and chocolate. Start a relationship with your local fish store and find out which types have the highest demand so that you can sell your juvenile plecos to them. For more information, see our article on breeding fish for profit.

4. The African Cichlid Tank

Male and female saulosi cichlids

Most African cichlids require larger fish tanks, but the saulosi cichlid (Chindango saulosi or Pseudotropheus saulosi) is a dwarf mbuna from Lake Malawi that only grows up to 3.5 inches (9 cm). They are very visually stunning because of the sexual dimorphism between males and females that makes them look like two different species. The dominant male is a vibrant blue with dark vertical stripes, while the females have a solid sun-yellow. Subdominant males are usually yellow to light blue, with some barring.

We recommend that you get 1-2 males and 4 to 5 females for a 40-gallon aquarium. They require high pH, high GH and KH as well as a high diet rich in vegetation and roughage. They also need lots of rocks and hiding spaces to minimize territorial disputes. Saulosi cichlids are very easy to breed, and you may see some of the females holding eggs in their mouths until the fry are free-swimming. You have two options: either move the fry to a separate tank, or allow them to stay in the rockwork until their bodies are strong enough for independent living. You should try the dwarf mbuna if you want an aquarium that is as fun and colorful as saltwater tanks.

5. The Rare Fish Colony

Trout goodeid

For our last stocking choice, we chose the trout goodeid (Ilyodon furcidens), a rarer type of livebearer from Central America that looks like a 3.5-inch (9 cm) miniature trout. They prefer a higher pH and GH than most livebearers. However, they need temperatures below 72 degrees F (22 degrees C). They aren’t picky eaters, but will happily eat any kind of food, including pellets, flakes, and hair algae, in your aquarium. You could mix them with other fish, but we like experiencing them as a single-species colony to see the unique behaviors that come out when they’re only surrounded by their own kind. Another good usage for a 40-gallon breeder aquarium would be conservation of endangered fish species. If you are interested helping to preserve at-risk fish, search online for the “CARES Preservation Program” to find out more.

These profiles for 40-gallon aquariums should be inspiring to you. You can also find many stocking ideas for 10-gallon or 20-gallon tanks. While Aquarium Co-Op does not ship fish, you can see our list of preferred online vendors that sell aquarium animals. Best of luck and enjoy nature daily!