Best Fish for 100 Litre Fish Tank

A 100 litre aquarium is where fishkeeping really starts to open up.

Unlike small tanks, you’re no longer limited to just a few nano species. You have enough space to create a proper, balanced setup with a variety of aquarium fish.

Many people search:

👉 “what fish can I keep in a 100 litre fish tank?”
👉 “best fish for 100 litre aquarium”
👉 “how many fish in a 100 litre fish tank?”

The answer is simple:

👉 You now have flexibility — but you still need a plan

A 100L fish tank gives you more options, but success still depends on choosing the right fish and building a balanced community.

Why a 100 Litre Fish Tank Is a Great Size

This is one of the most recommended tank sizes for beginners and intermediate fishkeepers.

It offers:

  • More stable water conditions
  • Greater stocking flexibility
  • Easier maintenance compared to small tanks
  • More choice of aquarium fish and tropical fish

👉 In short: fewer problems, more possibilities

What Fish Can Go in a 100 Litre Fish Tank?

At this size, you can start building a community aquarium.

That means:

  • Multiple species
  • Different swimming levels
  • Balanced behaviour

But not everything works.

Fish still need to be:

  • Compatible
  • Suitable in size
  • Appropriate for your setup

If you’re unsure about compatibility, review Aquarium Fish Compatibility Guide before choosing.

Best Fish for 100 Litre Aquarium Setups

Instead of listing random fish, it’s better to think in roles.

Mid-Water Schooling Fish (The Core)

These are the main visual focus of your tank.

They:

  • Swim in groups
  • Add movement
  • Create a natural look

These are some of the most popular tropical fish for aquariums and are widely available when you browse tropical fish selections.

👉 Always keep them in groups — this reduces stress and improves behaviour.

Bottom Dwellers (Balance the Tank)

These fish stay near the substrate and clean leftover food.

They:

  • Add activity to lower levels
  • Help maintain the tank
  • Create a more complete ecosystem

Feature Fish (Optional Centrepiece)

With a 100 litre tank, you can include:

👉 One standout fish

This gives your aquarium a focal point without overcrowding.

How Many Fish in a 100 Litre aquarium ?

This is one of the most searched questions — but there is no exact number.

It depends on:

  • Fish size
  • Activity level
  • Filtration
  • Maintenance routine

However, compared to a 30 litre aquarium:

👉 You can safely keep more fish — but only if balanced properly

For a full breakdown, see How Many Fish Can I Have in My Tank?.

A Simple Stocking Example

A well-balanced 100L aquarium might include:

  • A group of small schooling fish
  • A few bottom dwellers
  • One feature fish

This creates:

  • Movement
  • Balance
  • Low stress

👉 This approach works far better than randomly mixing species.

Why Overcrowding Still Happens in 100L Fish Tanks

Even with more space, beginners often:

  • Add too many fish too quickly
  • Mix incompatible species
  • Ignore adult size

This leads to:

  • Stress
  • Water quality issues
  • Behaviour problems

Feeding and Its Impact

With more fish comes more feeding — and more waste.

Overfeeding leads to:

  • Algae growth
  • Water instability
  • Poor fish health

This is why feeding must stay controlled (see How Often Should You Feed Aquarium Fish?).

Maintenance Still Matters

Even though a 100L aquarium is more stable, it still needs routine care.

A consistent schedule helps:

  • Maintain water quality
  • Prevent buildup
  • Keep fish healthy

Follow a routine like the one in Aquarium Maintenance Schedule (Weekly Routine).

Choosing the Right Fish for Your Setup

Instead of asking:

👉 “What fish can I fit in a 100 litre tank?”

Ask:

👉 “What combination of fish will stay balanced long-term?”

This prevents most problems before they start.

Common Mistakes to Avoid

  • Overstocking too quickly
  • Choosing fish based on appearance only
  • Ignoring compatibility
  • Skipping research
  • Adding large or aggressive species

Final Thoughts

A 100 litre aquarium gives you the opportunity to build a proper, balanced fish community.

It’s large enough to reduce common beginner problems, but still manageable for regular care.

If you plan your stocking carefully, your tank will be stable, visually appealing, and enjoyable to maintain.

If you’re ready to build your setup, you can browse buy aquarium fish, explore a wide range of tropical fish, or check available live fish for sale to find species suited to your aquarium.