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 cichlid hybrid is famous for its colorful patterns and large nuchal, which grows on male heads. 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 recommend keeping only one flowerhorn in a 40-gallon tank. As your pet grows, they will consume more food and need to be water changed frequently. 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 want to get one to three pairs of 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. 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 stocking list is a good starting point for your 40-gallon community aquarium. 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. Then we condition the adults for breeding by feeding plenty of their favorite foods, like Repashy gel food, sinking wafers, bloodworms, and blanched zucchini. The fry are smaller and prefer to eat live baby brine shrimps, driftwood, crushed flakes, canned green beans, and algae.

Long fin bristlenose plecos come in many varieties – such as albino, green dragon, chocolate, and super red. 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). The sexual dimorphism of males and women makes them appear like two distinct species. This is why they are visually amazing. The dominant male is a bright blue with dark vertical stripes. While the females are solid sunshine yellow. Subdominant males tend to range from yellow to light blue with faint barring.

For a 40-gallon tank, we recommend 1-2 males with 4-5 females. As with most Lake Malawi cichlids, they require high pH, GH, and KH, as well as a diet high 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 can either remove the fry into a separate grow-out tank or let them hide in the rockwork until they are big enough to fend for themselves. 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

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. Like most livebearers, they prefer higher pH and GH, but they are a bit unusual because they require temperatures cooler than 72degF (22degC). 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 40-gallon aquarium profiles should inspire you to get into the hobby. 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. We wish you all the best, and we hope that you enjoy your daily walks in the great outdoors!