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

Due to its dimensions of 36 inches long x 18 inches wide x 16 inches high (91x46x41 cm), the 40-gallon breeding aquarium is very popular. 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 New World hybrid cichlid is well-known for its jaw-dropping colors and large nuchal hump, which grows on the heads males. Flower horn fish are especially valued in certain Asian cultures because they are thought to bring good luck and prosperity. Although flowerhorns can be playful and friendly towards their owners, they can be quite aggressive towards other animals within their territory. We recommend keeping only one flowerhorn in a 40-gallon tank. Your pet will get larger and require more water changes as it eats a lot. 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. To minimize territorial disputes, make sure to provide plenty of aquarium plants and decorations to block line of sight. 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. Black phantom tetras are a favorite of ours (Hyphessobrycon gigalopterus) due to their strikingly high dorsal feathers.

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. To accommodate their larger wingspan, they require larger caves. 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. The fry have smaller mouths and often like to graze on driftwood, algae, crushed flakes, live baby brine shrimp, 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.

For a 40-gallon tank, we recommend 1-2 males with 4-5 females. They require high pH, high GH and KH as well as a high diet rich in vegetation and roughage. To avoid territorial disputes, they need plenty of rocks and hiding places. Saulosi cichlids can be very easy to breed. You may see the females holding eggs in the mouths of their fry until they are able to swim free. 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. If you are looking for a fun and enjoyable aquarium setup that rivals the brilliant colors of saltwater tanks, then you have to try this dwarf mbuna.

5. The Rare Fish Colony

Trout goodeid

We chose the trout goodeid, Ilyodon furcidens, as our final stocking choice. This rarer species of Central American livebearer looks almost like a miniature 3.5-inch (9cm) trout. Although they like most livebearers they prefer higher pH levels and higher GH. They also require temperatures lower than 72°F (22°C), which is unusual for them. They will happily eat pellets, flakes and hair algae from your planted 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. We have many more stocking ideas for 10-gallon and 20-gallon tanks for you to check out as well. While Aquarium Co-Op does not ship fish, you can see our list of preferred online vendors that sell aquarium animals. We wish you all the best, and we hope that you enjoy your daily walks in the great outdoors!