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5 Best Fish Tank Ideas for a 20-Gallon Aquarium

Getting a new 20-gallon aquarium is like starting with a fresh, blank canvas. There are so many possibilities when it comes to choosing the decorations, live plants, and of course aquarium fish. Here are five of our favorite setups to inspire you if you find yourself stuck in analysis paralysis due to all the options.

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. You don’t have to worry, this is a beautiful and simple setup that will amaze you every time it is displayed. The aim is to fill the aquarium’s rear half with plants in a variety of textures and colors. To maximize impact, drop in 12-20 neon Tetras. There’s something instantly mesmerizing about seeing a large group of identical fish swimming in an underwater forest of plants.

You can add some bottom dwellers to the aquarium to make them more interesting. For example, a colony of red cherry shrimp that stands out against the greenery, a few kuhli loaches for night cleaning, and a few nerite shells to control algae. You can keep your tank clean by choosing slow-growing plants and animals that aren’t likely to breed quickly. Because it’s not cluttered with different species, this tank looks more like a well-crafted piece of art. Its simplicity will make people think, “Why not have a tank like that?”

Neon tetras are brightly colored with red and blue stripes, which really make them stand out from a wall of aquatic plant life.

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. You should provide a pleco cave that the male can claim as his territory. 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.

After the fry have learned to swim, you can provide them with plenty of food such as Repashy gel food and flake food. You will need to change the water frequently if you want the fish to stay healthy. To decrease the buildup of nitrogen waste (and make the aquarium look better), consider adding live plants to the aquarium. 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. Your 20-gallon aquarium will be ready for your next breeding project.

To breed, you must have at least one male AND one female. Male bristlenose plecos tend to have a very bushy snout, whereas females have a smoother face.

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 brighter and can “dance” when they are around females. So make sure you have both genders in your aquarium.

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. They will happily lay eggs every day if you add lots of floating plants, moses, and other dense leaves. However, you won’t likely see any fry unless the eggs are removed. 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. You can use a sponge filter, or an airstone with plenty of plants to help them 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. When you feed the powder, the aquarium should get slightly cloudy with food particles visibly swirling in the water.

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. Also, consider adding some snails, amano shrimp, or cherry shrimp to clean up the food particles that fall to the substrate. If you’re searching for a different kind of community tank that will make people look twice, this weird, invertebrate-centric tank may be right for you.

If you notice your filter-feeding shrimp eating off the ground, it’s likely that they aren’t getting enough food. So increase their daily portions.

5. The Unheated Aquatic Aquarium

Looking for fish that can live in a 20-gallon tank with no heater? This danio aquarium might be the right choice if your room temperature is at least 62°F (17°C). 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.

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Danios swim at all layers of the aquarium, but you can add some other species that like cooler waters, such as five or six salt and pepper corydoras to pick up any food that gets past the danios. Cool-temperature invertebrates such as amano shrimp, Malaysian whistle snails and nerite snails would be good tank mates. (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.