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Best Fish for 10 Gallon Tanks

There’s a lot of things to consider when planning your first aquarium, and one of the most challenging might just be figuring out how to stock it. What are the best fish for a 10-gallon tank and how many fish can fit inside one? As you’ll see, there’s both an art and science to building a healthy freshwater tank, so check out these tips!

What You Need to Know When Stocking 10 Gallon Tanks

While 10-gallon aquariums have long been the most popular size for first-time fish keepers, they also present a few challenges as well. Novice aquarists can easily find advice on how to equip and maintain Nano Tanks, but it’s trickier to pick good fish for a 10-gallon tank and learn how to gradually build a new aquatic community.

Debunking the Inch-Per-Gallon Myth

You may have heard of the popular quasi-scientific rule for stocking a freshwater aquarium that goes something like “add one inch of fish per gallon of water.” Just add up the length of each fish, keep the total under 10-inches and you’re good, right?

Neon tetra fish with aquatic plant in aquarium

It’s not totally useless, but as a rule-of-thumb, it has some problems.

The inch-per-gallon guideline falls short because it’s overly simplistic. It ignores some essential but overlooked facts about aquariums that directly impacts how many fish you can safely keep inside a 10-gallon tank. Let’s take a look at what really matters when it comes to selecting the coolest freshwater fish for your 10-gallon tank.

Aquariums Hold Less Water Than You’d Think

10-gallon aquariums don’t actually hold 10-gallons of water, so if you’re using the inch-per-gallon calculation to stock your tank, the math will be off right from the start. This is one reason that many novices add too many fish to their new tanks and then suffer from heavy losses. How can this be?

Stunning reef aquarium.
  • Keep in mind that your tank’s substrate, decorations, and equipment take up space and reduce its water capacity.
  • It takes about 10 pounds of gravel to fill a standard 10-gallon or “leader tank” 3-inches deep, which displaces anywhere from 1.5 to 3 gallons of water.
  • Chances are good that you’ll only have about 8 gallons of free capacity left for your aquatic animals once you’ve assembled and filled your tank, and it definitely won’t be close to 10 unless you skip the substrate.

New Aquariums Can Maintain Fewer Fish Than Cycled or Mature Tank’s

The rule also assumes that all 10-gallon tanks can hold the same number of fish without problems. But the water chemistry in a brand new aquarium is very different from one that’s been cycled, and both are quite different from mature systems:

Nitrogen Cycle Diagram
  • It takes a few weeks for the good bacteria to become established and start regulating the Nitrogen Cycle in a new aquarium, so these tanks often experience wild and unpredictable spikes in ammonia and other toxins even when lightly stocked with hardy starter fish like Zebra Danios.
  • Once the water chemistry stabilizes (3 to 6 weeks), your tank is considered cycled and ready to handle a modest community of fish. But your chemistry may still fluctuate enough to stress-sensitive species like Neon Tetras, Fancy Guppies, and some freshwater invertebrates.
  • After 3 to 6 months, diverse populations of bacteria, algae and other organisms form a symbiotic matrix of biofilm throughout your mature aquarium, which further stabilizes the water chemistry and supports a larger community.

Ignores Filtration, Maintenance and Total Number of Animals

I’d also argue that your filtration system and maintenance routine has a much bigger impact on how many healthy fish you can keep in your small community than just the total length of fish. Even a 10-gallon with a single 1-inch fish will eventually crash if you neglect to filter and change the water:

Close-up betta filter baffle
Image Source : Green Jean
  • A 10-gallon with a robust HOB filter can reduce the bioload and support a larger community than one with an undergravel or cheap internal filter.
  • Frequent water changes can reduce the bioload in your tank and maintain a larger-than-ideal community, as long as the fish are not stressed from living in cramped conditions.
  • Even if your filter can handle the bioload, many fish get sick from stress if they’re surrounded by tank mates all the time, so the total number of animals matters, too.

What Types of Fish Can Live in a 10 Gallon Aquarium?

Activity and temperament are the key features in determining the best fish for a 10-gallon tank. Their size also factors in, but it’s not definitive. Minnows are small fish, for instance, but they are also very active and live in large schools, so they aren’t a good option for a 10-gallon. What should you look for?

Characteristics of the Ideal Nano Fish

Freshwater aquarium with plants and fancy guppies
  • Mellow, mild-tempered, and peaceful community species
  • Fish that are not very active or downright lazy
  • Animals that prefer to be on their own or don’t require large groups
  • Small (0.5 to 2.2 inches) and Medium (2.5 to 5.5 inches) sized fish with the above characteristics and similar water requirements 

Balance Your Community

You can often accommodate a larger community in a small tank if you add a mix of surface or mid-level swimmers and bottom feeders instead of fish that all use the same area. This reduces stress and competition, since they’ll mostly stick to different parts of your tank. Functional fish like algae eaters are a good idea, too!

Density and Calculating How Many Fish 

My advice for stocking your tank depends on your experience level and the stage and set-up of your aquarium. Here are some guidelines to help you calculate your ideal 10-gallon tank population:

Community Density

Lightly Stocked

Moderately Stocked

Densely Stocked

How Many Fish?

1 to 2 medium fish
3 to 6 small fish

1 to 3 medium fish
5 to 10 small fish

4 or more medium fish
12 or more small fish

Ideal for:

New or recently cycled tanks
First-time fish keepers

Cycled and mature tanks

Experienced fish keepers
Mature aquariums
Tanks with robust filtration and diligent maintenance

Community Density

Lightly Stocked

How Many Fish?

1 to 2 medium fish
3 to 6 small fish

Ideal for:

New or recently cycled tanks
First-time fish keepers

Community Density

Moderately Stocked

How Many Fish

1 to 3 medium fish
5 to 10 small fish

Ideal for:

Cycled and mature tanks

Community Density

Densely Stocked

How Many Fish

4 or more medium fish
12 or more small fish

Ideal for:

Experienced fish keepers
Mature aquariums
Tanks with robust filtration and diligent maintenance

How to Build Your Community Tank: 10-Gallon Tank-Mate Combos

It’s better to err on the side of caution when stocking a new tank to prevent deadly and expensive crashes. Once your tank cycles, you can gradually add more fish, and once it’s mature you can finish stocking your tank with the sensitive species ideal for established communities! 

Here’s a few examples of how your 10-gallon community can evolve over time:

Betta or Gourami Centered Tank

Initial Set-Up

1 Betta Fish OR
1 Dwarf Gourami 
1 Nerite Snail

Cycled Tank (~1 month)

2 to 3 Cory Cats
1 to 2 Otocinclus

Mature (3 to 6 months)

5 to 10 Shrimp w/ Male Betta OR
5 Neon Tetras w/ Female Betta OR
Additional Dwarf Gourami 

Initial Set-Up

1 Betta Fish OR
1 Dwarf Gourami 
1 Nerite Snail

Cycled Tank (~1 month)

2 to 3 Cory Cats
1 to 2 Otocinclus

Mature (3 to 6 months)

5 to 10 Shrimp w/ Male Betta OR
5 Neon Tetras w/ Female Betta OR
Additional Dwarf Gourami

Planted Loach Tank

Initial Set-Up

1 Kuhli Loach
1 Otocinclus

Cycled Tank (~1 month)

1 to 2 more Loaches
3 to 5 Fancy Guppies OR
4 Platy Fish

Mature (3 to 6 months)

1 to 2 Nerite Snails OR
5 to 10 Cherry or Ghost Shrimp

Initial Set-Up

1 Kuhli Loach
1 Otocinclus

Cycled Tank (~1 month)

1 to 2 more Loaches
3 to 5 Fancy Guppies OR
4 Platy Fish

Mature (3 to 6 months)

1 to 2 Nerite Snails OR
5 to 10 Cherry or Ghost Shrimp

Hard Water Community

Initial Set-Up

5 Least Killifish OR
3 Beckford’s Pencilfish OR
3 Molly Fish

Cycled Tank (~1 month)

5 more Killifish OR
5 more Pencilfish OR
3 more Mollys 
1 to 2 Nerite Snails

Mature (3 to 6 months)

5 additional Killifish OR 
5 Pencilfish OR 
3 Mollys OR
5 to 10 Cherry or Ghost Shrimp

Initial Set-Up

5 Least Killifish OR
3 Beckford’s Pencilfish OR
3 Molly Fish

Cycled Tank ( ~1 month)

5 more Killifish OR
5 more Pencilfish OR
3 more Mollys 
1 to 2 Nerite Snails

Mature (3 to 6 months)

5 additional Killifish OR 
5 Pencilfish OR 
3 Mollys OR
5 to 10 Cherry or Ghost Shrimp

15 Best Fish and Invertebrates for 10 Gallon Aquariums

Here’s a list of the top 15 fish for stocking 10-gallon freshwater aquariums. They’re all friendly, mellow species ideal for beginners and small set-ups, except the slightly more challenging Kuhli Loach and active Zebra Danio.

1. Betta Fish

fancy crowntail betta fish
Image Source: flickr.com

10-gallons is the ideal capacity for a Betta Tank, and you can easily keep a male or female Betta in a community with a few tank mates and some live plants. This is our favorite pick to start out with.

Species

Betta Fish (Betta splendens)

Size Range (length)

3.5 to 5.5 inches

Water Parameters

75 to 86°F
pH 6.0 to 8.0
Soft water 5 to 20 dGH

Tank Level

Middle and Top

Lifespan 

3 to 5 years

2. Dwarf Gourami

Dwarf gourami on a blurred background (Trichogaster lalius)

The magnificent Dwarf Gourami comes in a rainbow of colors and makes a stunning centerpiece to a 10-gallon community. They’re easy-going, and you can keep up to 3 of these bigger fish in your tank.

Species

Dwarf Gourami (Trichogaster lalius)

Size Range (length)

3.5 to 4.5 inches

Water Parameters

77 to 79°F
pH 6.0 to 8.010 to 20 dGH

Tank Level

Middle

Lifespan

up to 5 years

3. Neon Tetra

Neon Tetra
Image Source: flickr.com

The beautiful red-and-blue Neon Tetras are an easy and popular option for small tanks. They’re sensitive and do better in cycled and mature communities, and are best kept in groups of 6 to 10 in a 10-gallon.

Species

Neon Tetra (Paracheirodon innesi)

Size Range (length)

1 to 1.5 inches

Water Parameters

70 to 81°F
pH 6.0 to 7.0
Soft water under 10 dGH

Tank Level

Middle

Lifespan 

up to 10 years

4. Zebra Danio

zebra danio (stripe)
Image Source: flickr.com

Zebra Danios are hardy and active fish ideal for new aquariums, but you’ll likely need to upgrade their habitat as they mature.10-gallons are a bit cramped for adults, and these fish prefer larger groups of 15+.

Species

Zebra Danio (Danio rerio)

Size Range (length)

1.5 to 2 inches

Water Parameters

64 to 77°F
pH 6.0 to 8.0
Soft or hard water

Tank Level

Middle

Lifespan

3 to 5 years

5. Fancy Guppy

Guppy in freshwater aquarium. Poecilia reticulata.

The sensitive Fancy Guppy prefers cycled and mature tanks, but these colorful small live-bearing fish are easy for beginners to care for (and breed)! Add a few for a spark of color or keep 8 to 15 adult fish in a group.

Species

Fancy Guppy (Poecilia reticulata)

Size Range (length)

1 to 2.5 inches

Water Parameters

75 to 82°F
pH 5.5 to 8.58 to 12 dGH

Tank Level

Middle and Top

Lifespan 

3 to 5 years

6. Platy Fish

Sunset Variatus Platy fishes inside aquarium.
Image Source : flickr.com

Another easy-breeding and colorful live-bearer is the Platy Fish, and you can keep up to 5 adults in a 10-gallon tank or a group of 3 in a mixed community. They’re a good option if you have hard water, too.

Species

Platy Fish (multiple Xiphophorus sp.)

Size Range (length)

2.5 to 3 inches

Water Parameters

72 to 70°F
pH 7.0 to 8.0
Hard water 10 to 28 dGH

Tank Level

Middle

Lifespan

3 to 4 years

7. Common Molly 

Mollies (Poecilia sphenops)
Image Source : flickr.com

The live-bearing Common Molly requires hard water, but otherwise is undemanding and easy to care for. You can keep these fish solo or in groups up to 4 in a 10-gallon, but avoid the bigger Sailfin morph, which needs more space.

Species

Common Molly (Poecilia sphenops)

Size Range (length)

up to 4.5 inches

Water Parameters

72 to 82°F
pH 6.5 to 8.0
Hard water 15 to 30 dKH

Tank Level

Middle

Lifespan

3 to 5 years

8. Least Killifish 

Isolated Least Killifish.
Image Source : wikimedia.org

Least Killifish are a unique micro-fish ideal for communities with freshwater shrimp and snails. They often can’t compete with bigger fish, but you can keep up to 20 of them in a 10-gallon tank!

Species

Least Killifish (Heterandria formosa)

Size Range (length)

0.8 to 1.4 inches

Water Parameters

68 to 79°F
pH 7.0 to 8.0
Hard or soft water

Tank Level

Middle

Lifespan

3 to 5 years

9. Dwarf Pencilfish 

Isolated Red Pencilfish
Image Source : wikimedia.org

Dwarf or Beckford’s Pencilfish are one of the few species of pencilfish ideal for novice aquarists and small set-ups. They have an entertaining way of darting around your tank and are available in vivid red and golden morphs 

Species

Beckford’s Pencilfish (Nannostomus beckfordi)

Size Range (length)

1 to 1.5 inches

Water Parameters

76 to 82°F
pH 6.5 to 7.2
Soft or hard water

Tank Level

Middle

Lifespan

3 to 5 years

10. Otocinclus Catfish

Otocinclus macrospilus
Image Source: wikipedia.org

One of the most functional fish in the trade is the algae-eating Otocinclus catfish or Oto! They’re a great 10-gallon option, either individually or as a group, and they’ll keep troublesome algae at bay too. 

Species

Otocinclus (multiple Otocinclus sp.)

Size Range (length)

1 to 2 inches

Water Parameters

72 to 82°F
pH 6.0 to 7.5
Soft water under 15 dKH

Tank Level

Mostly Bottom

Lifespan

3 to 5 years

11. Dwarf Corydoras Catfish

Dwarf corydoras
Image Source : wikimedia.org

Scavenging Corydoras or Cory Cats are fun bottom dwellers, but they’re shy as singles and prefer to live in groups of 4 to 8. The Dwarf Cory is a great option for a 10-gallon, but the slightly smaller Pygmy Cory has similar requirements.

Species

Dwarf Cory Cat (Corydoras hastatus) 
Pygmy Cory Cat (Corydoras pygmaeus)

Size Range (length)

1 to 1.5 inches

Water Parameters

72 to 79°F
pH 6.0 to 7.2
Soft water under 15 dGH

Tank Level

Bottom

Lifespan

3 to 5 years

12. Kuhli Loach

Banded Kuhli Loach Live Fish Aquatic Pets

Once you’re comfortable maintaining an aquarium, you can try the slightly more challenging Kuhli Loach. They tend to be shy and don’t come out by day, but if you have a moonlight, you can watch them scavenge at night!

Species

Kuhli Loach (Pangoi kuhlii)

Size Range (length)

3 to 5 inches

Water Parameters

75 to 84°F
pH 6.0 to 7.0
Soft water 2 to 10 dGH

Tank Level

Bottom

Lifespan 

up to 10 years

13. Nerite Snails

Imperial Tropicals 2 Tiger Nerite Snails (Neritina natalensis)

Once your tank has cycled, consider adding a Zebra, Tiger, or Olive Nerite Snail to your clean-up crew. They’re an ideal option for hard water communities and they’ll likely reproduce in your tank, too.

Species

Nerite Snails (multiple Neritina sp.)

Size Range (diameter)

0.5 to 2 inches

Water Parameters

72 to 78°F
pH 7 to 8.4 (8.1 ideal)
Hard water 6 to 12 dKH

Tank Level

All

Lifespan

1 to 2 years

14. Red Cherry Shrimp

Cherry Shrimp (Neocaridina davidi)

Red Cherry Shrimp (RCS) are brightly-colored freshwater invertebrates perfect for small hard water set-ups. They’re sensitive to nitrites and do best in mature 10-gallons, but they’re an easy and fast-breeding option for beginners.

Species

Red Cherry Shrimp (Neocaridina heteropoda)

Size Range (length)

1 to 1.5 inches

Water Parameters

65 to 85°F
pH 6.5 to 8.0
Hard water 6 to 10 dGH

Tank Level

Bottom

Lifespan 

1 to 2 years

15. Ghost Shrimp

KOOL TOOLS 21 Freshwater Ghost Shrimp (Glass Shrimp, Ghost Shrimp)

Another freshwater invertebrate that looks cool in a small tank is the Ghost or Glass Shrimp. They’re easy to care for, and you can see straight through their carapace and even watch them digest their food! 

Species

Ghost Shrimp (multiple Paleomonetes sp.)

Size Range (length)

1 to 1.5 inches

Water Parameters

65 to 82°F
pH 7.0 to 8.0
Hard water 5 to 8 dGH

Tank Level

Bottom

Lifespan

1 year

Conclusion

There’s more to stocking a 10-gallon than just the size of your fish, and I hope this article has helped you get a sense of how to stock your tank as it matures. What is your favorite fish for 10-gallon tanks? Comment below, or come join the big social media pond online!

Best Fish for 10 Gallon Tanks - Infographic

Jen has more than 30 years experience as a biologist, aquarist, and fishkeeper. She is an expert in setting up new tanks and maintaining naturally-planted freshwater habitats, and has experience raising a wide variety of aquatic species.

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