5 Best Fish Tank Ideas for A 20-Gallon Aquarium

5 Best Fish Tank Ideas for a 20-Gallon Aquarium

It’s like starting from scratch when you buy a 20-gallon new aquarium. There are so many possibilities when it comes to choosing the decorations, live plants, and of course aquarium fish. If you’re stuck in analysis paralysis from all the choices, here are five of our favorite setup ideas to help inspire you.

1. The Aquarium with the “I Just Want It to look Good”

If you are not an expert aquascaper, or a creative artist, it might be difficult to create an exquisite design for your aquarium. This first setup is simple, but it’s a stunning show-stopper every time you look at it. You want to fill the aquarium’s back with plants of different textures and colors. This could include stem plants, vallisneria or dwarf aquarium lilies. For maximum impact, add a group of 12-20 neon tetras. There’s something instantly mesmerizing about seeing a large group of identical fish swimming in an underwater forest of plants.

Because neon tetras prefer to swim in the middle, you might add a few bottom dwellers. These include a red cherry shrimp colony to pop against the greenery and three to four kuhli locaches to clean the tank at night. For minimal maintenance, you should choose slow-growing plants or animals that don’t reproduce too fast. This tank is attractive to everyone because it doesn’t have a lot of different species, but instead looks like a carefully crafted piece of art. The simplicity of its beauty will get people thinking, “Why don’t I do a tank like this?”

Neon tetras have bright blue and red stripes that really stand out against a wall of aquatic plants.

2. The “Fish Breeding” Aquarium

Setting up a dedicated tank for breeding fish is enjoyment for the whole family. You can teach kids about nature, get your partner more interested in aquariums, and even sell the offspring to your local fish store or other hobbyists for profit. Most people start with livebearers (or fish who bear live young) like guppies or platies, but have you ever considered breeding bristlenose (or bushynose) plecos before? They are so easy-to-breed that many varieties, such as the wild-type, albino, super-red, and long-fin bristlenose plecos, have been developed. The male will claim his own territory by providing a pleco cave. For spawning, give the male and female plenty of healthy foods such as Repashy gel foods and frozen bloodworms. Then the male will entice the female to his cave, trap her inside to lay eggs, and faithfully fan the eggs (to increase water flow) until they hatch. You can place the parents in an aquarium that is larger than your home. After the babies hatch, move them all into your 20 gallon tank.

Once the fry are freely swimming, provide plenty of food in the form of Repashy gel food, flake foods, canned green beans, frozen baby brine shrimp, and even algae in your tank. You will need to change the water frequently if you want the fish to stay healthy. Adding live plants to your aquarium can help reduce nitrogen waste buildup and make it look better. Anubias and Java fern attached to driftwood provide cover and food for the babies. Once they are about 2 inches (5 cm) long, you can move a few of your favorites to other aquariums to help with algae control and sell the rest to your local fish store. Now your 20-gallon aquarium is ready for the next breeding project.

In order for breeding to occur, you need at least one male and one female. Female bristlenose plecos are more rounded than males.

3. The Rainbowfish Aquarium

Most rainbowfish are too big to fit comfortably in a 20-gallon fish tank, but it’s the perfect size for rainbowfish in the Pseudomugil genus and other dwarf rainbowfish that remain under 2-2.5 inches (5-6.3 cm) long. Some of the most popular species include the neon red (P. luminatus), forktail blue-eye or furcata (P. furcatus), spotted blue-eye (P. gertrudae), Celebes (Marosatherina ladigesi), and threadfin rainbowfish (Iriatherina werneri). The males are more colorful and will “dance” in the presence of females, so get both sexes for your aquarium to see this unique behavior.

As surface-dwelling fish, rainbowfish inhabit the top one-third of aquariums, so make sure to have a tight-fitting tank lid that prevents them from jumping out. You can add lots of floating plants and mosses to encourage them to lay eggs daily, although you may not see any fry until you take out the eggs. Because of their small mouths, feed them tiny floating or slowly sinking foods, such as baby brine shrimp, daphnia, cyclops, crushed flakes, micro pellets, and Easy Fry and Small Fish Food.

Dwarf rainbowfish can be a tad more expensive at $10 to $15 each, and ideally you want a school of six or more. To fill out the rest of the tank, you can get other community fish like small tetras and rasboras that swim in the middle and corydoras and snails that scavenge at the bottom. (Cherry shrimp may get picked on since rainbowfish are active creatures that love to eat.)

While dwarf rainbowfish can be a little harder to source, keep searching because their gorgeous colors and lively behavior are worth the hunt.

4. The Oddball Aquarium

Most people think of oddballs as rare or interesting fish, but what about keeping an oddball invertebrate? Filter-feeding shrimp – like the bamboo or wood shrimp (Atyopsis moluccensis) and vampire shrimp (Atya gabonensis) – have large, feathery mitts on their hands that are made for catching and eating small particles floating in the water. Because of the way they feed, don’t set up a powerful hang-on-back (HOB) or canister filter that polishes all the little crumbs from the water. Instead, go with a gentle sponge filter or maybe just an air stone with lots of sturdy plants for them to climb on. Next, give them powdered foods such Hikari First Bite, Repashy gel foods (in its raw powder form), or specialty foods for filter feeding shrimp. You should notice food particles in the aquarium’s water when you add the powder.

For a 20-gallon fish tank, you can get one to two bamboo shrimp and one vampire shrimp. The shrimp grow rather large, ranging from 3-6 inches (8-15 cm) each, so you want them to stand out as the centerpieces of the aquarium by pairing them with nano fish like celestial pearl danios, Norman’s lampeye killifish, and chili rasboras. To clean up food particles from the substrate, you might also consider adding snails, amano shrimp or cherry shrimp. This weird, invertebrate-centric community tank might be the right choice for you if you are looking for something different.

If you see your filter-feeding shrimp scavenging on the ground, they’re likely not getting enough food, so increase their daily portion size.

5. The Unheated Aquarium

Looking for fish that can live in a 20-gallon tank with no heater? If your room temperature is 62degF (17degC) and above, then this danio aquarium may be the perfect choice. Danios are a highly active, torpedo-shaped fish that come in many varieties and colors, such as zebra, leopard, long fin, and even Glofish. You can get anywhere from 12 to 15 to make a kaleidoscope, zooming around your tank and getting wild during feeding times.

Danios will swim in any aquarium layer. But, you can also add other species to cooler waters. For example, five to six salt-and pepper corydoras are able pick up food from the aquarium’s bottom. Some cool-temperature invertebrates that would work as tank mates include amano shrimp, Malaysian trumpet snails, nerite snails, and Japanese trapdoor snails. (When keeping snails, make sure they get enough minerals in the water and are fed some calcium-based foods.) If you want an action-packed, beginner-friendly tank full of hardy fish, you can’t go wrong with an aquarium of danios.

Long-fin zebra danios have a high energy, beautiful design, and are affordable.