Custom Fish Tanks

What are the Best Fish for a Small Aquarium?

If you’re new to the world of fish keeping, it’s daunting to figure out which fish are the best for your small fish tank. There are many different fish species, each possessing its own characteristics and unique look. Some are antisocial and territorial, while others are community fish that do well in groups.

Nano or small fish tanks have become prized possessions in recent years. They are elegant, space-saving, and the perfect starter aquarium for a beginner fish keeper. But which fish should you put in your newly installed nano aquarium? Here are 10 of the best fish for a small aquarium:

  1. Betta Splendens (Siamese fighting fish)

Although Betta Splendens or Siamese fighting fish were bred for aggressive, one-on-one combat, they can fit quite nicely in a newly installed aquarium. A male Betta is wonderful, with long fins that flow gracefully behind him as he swims. Females, while also gorgeous, don’t exclude the same vibrant colours.

When putting your Betta in a small fish tank, be sure to only put one per tank as they’re an antisocial species. Add a few caves or live plants for your fish to hide in and just like other fish, ensure the water is well-filtered and regularly changed.

Just a warning: Bettas, if confined to smaller spaces, can be aggressive to their owners. So if you have small kids in the house, a Betta might not be the best fish for your tank.

  1. Harlequin Rasbora

Hailing from Southeast Asia, these tiny fish are a great addition to any freshwater nano fish tank and a staple among aquarists. They prefer to live in groups, so ensure to buy at least six of them as any less can cause stress.

While these little guys only grow to be about 2 inches long, they make up for it with their playful and social personality. They’re also stunning to look at,  with their brightly coloured scales that exude black and orange shades. Harlequin Rasbora also resemble tiny goldfish, making them a familiar and popular choice for small fish tanks.

In addition to their small stature, this species is relatively easy to take care of. Waters should remain at approximately 73 to 82 degrees with a PH of 6.0 to 7.5. As long as these water parameters are met, your Harlequin Rasboras should stay healthy and thrive in your nano fish tank.

  1. Apistogramma

If you’re planning on having your aquarium inhabit several species of fish, then the Apistogramma is a must. These peaceful, friendly species do particularly well in groups, so they should have no issues mixing in with other fish. Apistogramma fish also prefer to stay near your substrate, or on your aquarium’s floor and even love to dig! Because of this tendency, you’ll want to add a sand substrate to your tank.

Besides their social nature, these little fish have beautiful, vibrant colours that are sure to stand out in your aquarium. They come in various shades, such as yellow, blue and red, and have stunning patterns on their bodies. The Apistogramma is a perfect fish if you want to add personality and colour to your nano tank.

In terms of fish care, ensure your tank has a temperature of 70 to 80 °F and a pH level of 6 to 7.

  1. Fancy Guppy

Few fish species radiate beauty and glitz like the Fancy Guppy. As their name suggests, Fancy Guppies are a more impressive variety of the common Guppy, being more comprehensive and far richer in colour. Their tails have various colour shades and designs, with some even having spots!

Fancy Guppies are an ideal fish for 5-gallon tanks as they’re easy to take care of. They’re relatively small, with females maxing out at 2.4 inches and males 1.4 inches, and are friendly creatures, so they do great in groups. As long as you have at least 6 of them, they should be quite content and happy in your aquarium.

If you’re having trouble telling apart a male and a female, simply assess their tails. Males have long and narrow anal fins with a pointed end as it’s required to spread their sperm, while females have a shorter anal fin that’s triangular. If you still can’t tell, simply ask your local fish store for assistance.

Regarding water quality, Fancy Guppy fish prefer higher temperatures of around 74 to 82 °F with a pH level above 7. They are tropical fish, so they prefer relatively warm waters.

  1. Bumblebee Goby

You’ve probably noticed by now that many of the best fish for small tanks are tiny! And the Bumblebee Goby is no different. In fact, this little guy only grows to be about 1.5 inches!

Despite their small size, Bumblebee Gobies stand out in any aquarium – big or small. Their yellow and black stripes make them look like, you guessed it, a bumblebee! They’re active fish that love exploring their surroundings and can be seen at the bottom of your water column. But, despite being very peaceful fish, they are pretty territorial and will protect their designated area in the tank.

Because they are brackish water fish, your nano tank will need marine salt to maintain the correct water quality. The specific gravity (amount of dissolved salts) should be between 1.002 and 1.006 and the water temperature should be between 72 to 84, or more ideally 73.5 to 79. Ph levels, meanwhile, should range from 7 to 8.5, with water hardness being between 9 and 19 dKH.

Like any fish, you want to emulate their natural environment in your aquarium. So, include some plants and rocks to hide in and feel safe. You should also have a sand substrate, as they’re considered bottom-feeders and will often scavenge and dig for food in the sand. Thus, you’ll want to avoid gravel substrate as it can irritate their delicate gills.

  1. Zebra Danios (Zebrafish)

These adorable little fish have pyjama or zebra-like stripes and are native to southern Asia and belong to the minnow family of Cypriniformes.

Zebrafish are very popular among aquarists because of their small size (1.5 inches), unique markings, and friendly personality. They are considered schooling fish, meaning you’ll need at least 5 to maintain their social structure – any fewer and they will become aggressive to other species. But, the more, the merrier as they love to shoal together.

These fish species are adaptable and can thrive in various temperatures and PH levels. Combined with their social nature and beautiful stripes, they’ve become a staple in many nano and freshwater aquariums. Just ensure you have vegetation and decorative objects to hide in as they are pretty shy!

  1. Least Killifish

Native to the United States, these fish are part of the livebearer family and typically can be seen throughout Louisiana and South Carolina. Known for their small stature, Least Killifish only grow to be only 0.8 inches and 1.4 inches for males and females, respectively. These small freshwater fish are ideal for beginners with small fish tanks, and a sight to behold once they move together in unison.

Least Killifish are shy and considered prey, meaning they often hide away from other aggressive fish. As a result, they’re often best in a single-species tank in groups of at least 3 (2 females and 1 male) or more, allowing them to feel more comfortable. They also shoal in groups as a means of protection.

Killifish are known for being jumpers, so you should have a tight-fitting lid on your aquarium. But because of their small size, a hood that isn’t fully secured may have enough space for them to escape.

  1. Neon Tetra

The Neon Tetra is a hardy little fish that’s known for its dazzling colour. Starting from its nose, down to the adipose fin, you’ll see a neon blue stripe. Underneath the blue stripe is their silver belly and a red line that goes to the tail’s base. These bright varied colours make them a popular choice for many freshwater aquariums.

Despite their small size, only reaching about 1.5 inches, Neon Tetras can be aggressive under the right circumstances. If they’re not matched with suitable tank mates or if they’re feeling threatened, they may start to nip at other fish. As a result, it’s best to keep them with other small, peaceful fish. They also shoal in groups, so it’s recommended to keep them in schools of at least six.

When it comes to water quality and feeding, Neon Tetras are relatively easy to care for. Ensure you keep temperatures between 75° and 80° degrees Fahrenheit and maintain a pH between 6.8 and 7.8. They’re also not picky eaters as they eat a wide variety of foods, including dried bloodworms and brine shrimp, flake food and small granules.

  1. Platy

The Platy species is a freshwater fish native to Central America and Southern Mexico. These friendly and pleasant fish allow aquarists to mix them with other peaceful species. They’re also a good option for beginner fish keepers and intermediates alike, as they are wide varieties which come in various colours and patterns.

Platies are schooling fish, meaning they should be kept in groups of at least five or more. They’re also known to be livebearers, which means the females retain eggs inside their bodies and give birth to living young.

When it comes to fish care, they’re considered easy to care for and aren’t too picky regarding food. They’re omnivores, meaning they’ll eat almost anything, including pellets, flakes, freeze-dried food, live/frozen food and vegetables. Because they eat a wide variety of food, they’re also a good option for a community tank.

One thing to keep in mind is that Platies are notorious jumpers and will escape your tank if you aren’t mindful. Always ensure your fish tank lid is tightly secured and without any gaps.

  1. Honey Gourami

If you need to spruce up your tank and add real pop, then the Honey Gourami is perfect for you. These iridescent fish are brightly coloured, coming in yellow and orange shades, with males being more vibrant than females. Their size is also slighter bigger than average on this list, reaching a maximum length of 2.2 inches, which makes them ideal for smaller fish tanks.

When it comes to their temperament, Honey Gouramis are typically peaceful and playful at the same time. However, like other proud fish, males can often fight with each other for dominance. If you want to avoid this, keeping them in pairs or groups with more females than males is best.

Once you’ve purchased your Honey Gouramis, setting a higher-than-average temperature for them to live in is important. They’re native to tropical areas and prefer water that’s between 78°F to 82°F with a pH level of 6.0-7.5. Lighting should also be dim to moderate.

  1.  Celestial Pearl Danios

Celestial Pearl Danios are incredibly tiny, growing to only 0.75 to 1 inch in length when fully grown. These nano fish are perfect for small, low-maintenance aquariums as their natural habitat is shallow, slow-moving water with surrounding plants. This can be emulated in a fish tank by having floating plants and low levels of lighting.

When it comes to appearance, their massive beady eyes and circular bodies are uniquely beautiful and make them a standout among fish. They also have a distinctive pattern on their bodies which resembles a galaxy, giving them the trade-industry name Galaxy Rasbora.

Unlike other smaller fish, Celestial Pearl Danios are not schooling fish. However, while they may not swim together, they find comfort in larger groups and should be kept in an aquarium with at least six other fish.

These little guys are naturally peaceful and get along well with other species. However, males tend to be aggressive and fight each other over females, quickly turning your aquarium into a war zone. And since these fish become sexually mature at 3-4 months old, it’s important to monitor their behaviour and separate them if necessary. However, we always suggest keeping your male population at a minimum to prevent any issues.

  1. Rummy Nose Tetra

The Rummy Nose Tetra are native to South America and an excellent addition to Nano tanks. Known for their transparent bodies, deeply coloured heads and patterned tails, these little fish are a real treat. Infact, if you look hard enough, you can see their bones – how cool is that?

If you are unsure how many Rummy Nose Tetras to get, a good rule of thumb is one fish per two gallons of water. So if you have a 20-gallon fish tank, you could get 10 of these little guys. Because they’re a passive species, they require at least five fish to feel comfortable and secure in their environment.

As for care, Rummy Nose Tetras are considered to be easy. They’re typically seen in the middle of your water column and will only travel to the top to feed. This means you don’t need to worry about having too many plants or decorations in your tank as they won’t bother them.

Like Platies, the Rummy Nose is an omnivore and will eat various foods, including flakes, pellets, freeze-dried food and live/frozen food. They’ll also eat leftover food, so there’s no need to worry about over-feeding them.

  1. White Cloud Mountain Minnows

White Cloud Mountain Minors was once referred to as “the working man’s neon” as they offered much of the same beauty of neon tetras at a fraction of the price. These fish are small, only growing to be about 1.5 inches, with males having a more slender look than females.

They have an iridescent bronze-brown body with a fluorescent stripe that runs along their lateral line, from their head all the way to their tail. These fish species come in various colours and contrast beautifully against a planted tank and other species. Due to their size and vibrant colours, they’re extremely popular among aquarists.

White Cloud Mountain Minnows are schooling fish and should be kept in groups of 6 for smaller tanks. However, larger tanks can hold groups of up to 10 and typically do well with other community fish.

Unlike other freshwater fish, White Cloud Mountain Minnows prefer cooler water and should be kept in an aquarium with temperatures between 65-77°F or 18-25°C . As such, they can easily live in an unheated fish tank, saving you some money on energy costs. However, if water does get too warm, it can cause these fish to become stressed, making them more susceptible to disease.

Critters You Can Include in Your Small Fish Tanks

Colourful tiny fish who gracefully swim in unison is the first thing that comes to mind when most people think of fish tanks. But did you know other small pets can share your freshwater aquarium? 

Let’s go through a few other companions you can include in your small fish tank:

African Dwarf Frog

The African Dwarf frog is native to tropical areas of Africa and is a popular pet for beginner fish keepers. These frogs are fully aquatic, meaning they live their entire lives in the water and do not require land to bask on. They’re also very sociable and can live harmoniously with other small fish, snails and shrimp.

African Dwarf Frogs are generally peaceful creatures but can sometimes appear aggressive towards each other. However, this may be due to the mating process or when they attempt to crawl over each other. 

Like other frog species, they love to jump and will escape your tank if you’re not careful. Always make sure your aquarium is covered and secure to prevent any accidents.

Ghost Shrimp

These invertebrates are often kept as pets for their interesting, transparent appearance and affordability. They’re also tiny, only reaching a maximum length of 2 inches as adults, which makes them ideal for nano tanks.

These little guys are actually scavengers that help clean your aquarium by eating leftover food of algae and other debris. If you have other fish, you don’t have to worry about overfeeding as the shrimp will simply eat their leftovers. However, you still need to feed them a diet consisting of larvae, weeds, aquatic plants, algae wafers and pellet fish food.

Due to a ghost shrimp’s delicate exoskeleton, they’re particularly vulnerable when shedding their shells. During this time, keep them away from boisterous fish that may view them as an easy meal. This shouldn’t be too much of a problem since ghost shrimp are naturally antisocial and prefer to stay hidden away in plants or decoration.

In addition to aggressive fish, also be sure not to have any sharp objects, i.e. decorations with pointy edges in your tank as it can easily injure or kill them.

Nerite Snails

Nerite snails aren’t just great to look at and widely available to buy; they’re also highly practical little creatures that help keep your aquarium clean. These snails are known as algae eaters and will graze in algae, diatoms, uneaten food and aquarium detritus. This makes them the perfect cleanup crew for small tanks as they minimise water waste products that affect fish health.

In terms of behaviour, Nerite snails are peaceful and somewhat docile. But despite being slow-mowing, they can freely move across your fish tank without too much trouble. 

You might only have issues if you have other fast-moving fish that may view them as potential prey. If you ever buy them from a pet store, ensure they’re not already being kept with any fish that may eat them.

Type of Fish to Avoid for Your Small Aquarium

When setting up a small aquarium, the main thing to avoid is fish that grow too large. Many fish keepers buy small fish without realising how big they’ll eventually get and get stuck with an overcrowded tank. 

Below are some examples of fish that grow too large for small aquariums:


This is the centrepiece of many aquarium tanks, admired for their graceful swimming and beautiful fins. However, many people don’t realise that Angelfish can grow up to 10 inches in length. So, if you’re taking care of two angel fish, you’ll need a 29-gallon tank.

African Leaf Fish

There are few fish species as exotic in looks as the African Leaf Fish. They can change colours and even camouflage themselves to hide from predators. However, while they’re small in stature initially, they will eventually grow to be about 8 inches long.


This large and aggressive species that can grow up to a foot long! This fish species lives for around 20 years and is considered predatory in nature. They’re not a good choice for small tanks as they require a lot of swimming space and can quickly outgrow their environment.

Silver Dollar

While the Silver Dollar fish’s size is nothing to write home about at 6 inches across, it’s their quantity that’s the issue. They’re schooling fish, meaning you’ll need at least 4-6 of them to feel comfortable in their environment. This quickly takes up a lot of space in a small tank and is not ideal if you’re looking for a low-maintenance aquarium.

Frequently Asked Questions

Can you have too many fish in an aquarium?

Yes, you can have too many fish in an aquarium. Overcrowding can quickly become a nuisance in smaller tanks as there’s less water to dilute waste and toxins. This can lead to many health problems for your fish, inducing stress which can stunt growth and lower their immunity.

If your groups of fish have outgrown their tank, consider buying a larger tank or rehoming some of your fish to make more space.

Is it ok to keep a fish in a small tank?

Absolutely! Some species thrive in small tanks as long as they’re compatible with their tank mates. If your fish tank is smaller, just be mindful when adding more fish as they may outgrow their environment. You’ll also want to employ a proper maintenance schedule to maintain your tank’s living conditions.

What kind of fish can live in a 1 gallon tank?

Aquarium owners looking to have a mini aquarium can opt for goldfish or a guppy if there are at least two fish. The general rule of thumb for fish tanks is to have 1 gallon per 1 inch of fish, so the smaller the fish , the more you can have in your tank. 

However, always remember that many tiny fish are schooling fish and will need to be in a group of at least 4-6 fish to feel comfortable. If you’re a dedicated aquarist who loves fish, there are few things sadder than a  single fish swimming aimlessly in a tank by itself.

What kills fish in a tank?

Waste buildup, low oxygen levels and high ammonia levels are all common causes of fish death in tanks. You can often avoid these problems by doing regular water changes and removing rotting food and dead fish left for long periods. As long as you’re vigilant about maintaining your tank, you should be able to avoid these problems.

Can betta fish live in a 2-gallon tank?

Betta fish should live in a minimum tank size of at least 2 gallons. A smaller tank will experience rapid water quality and temperature changes due to it having not enough water.

While betta fish can live in confined spaces, it’s also not the best environment for them. A 2-gallon tank is a bare minimum, but we suggest getting a larger tank if possible to give your fish more room to swim and explore. Otherwise, they may become aggressive or stressed, leading to health problems.

What are the advantages of  a small aquarium?

Smaller tanks have a few advantages over large tanks. They’re often cheaper to buy and set up, and they’re easier to install since they don’t require as much space. In addition, they’re often easier to maintain since water changes are quicker and less difficult to do.

Despite these advantages, smaller tanks also have a few disadvantages. They’re more prone to water quality issues since there’s less water to dilute, can’t inhabit as many fish and experience changes in water chemistry and temperature much faster. As a result, they require more attention and care to ensure the health and wellbeing of your fish.

What is the best aquarium fish for small tanks?

While many of the above fish would be a great addition to a small aquarium, we recommend Neon Tetra and Zebra Danio.

Final Thoughts

Small tanks are the month’s flavour, with more and more people opting for them over the traditional 20-gallon aquarium. While a small tank might have its benefits, you need to be mindful of the fish you’re adding to ensure they’re adequately suited for their environment.

If you are unsure when purchasing your fish, always ask the store employee for suggestions on which fish would be best for your tank size. With a little research, you can have a thriving and healthy small aquarium in no time!

Top-rated Aquarium Installation by Sidepost

Whether you need a new fish tank for your home or office, our professional fish tank builders and installers at Sidepost can help. We offer a wide variety of aquarium installation services to suit your needs and budget across Australia. We also carry all the necessary supplies to get your new fish tank firing at all cylinders and even provide maintenance services to keep it running smoothly.

If you’re looking for an experienced and professional team to install your new fish tank, contact us at 1300 138 499 or book online. We service all across Australia, including Sydney, Melbourne, Brisbane, Perth, Adelaide, Newcastle, Gold Coast and Canberra.