Best Fish and Plants for the Fluval Flex Aquariums

The Fluval Flex is one of the most popular aquarium ranges for both beginners and experienced aquarists. With its distinctive curved front glass, integrated filtration, remote-controlled LED lighting, and compact all-in-one design, it offers an excellent foundation for a stylish freshwater aquarium.

Whether you own a Fluval Flex 34L, 57L, or 123L, choosing the right fish and plants is essential. The best livestock will suit the aquarium’s size, filtration capacity, swimming space, and water conditions, while the right plants will help create a natural, healthy, and visually striking display.

In this guide, we’ll explore the best fish and plants for Fluval Flex aquariums, along with stocking tips, aquascaping ideas, and beginner-friendly combinations.

Why the Fluval Flex Is So Popular

The Fluval Flex range is designed to make aquarium keeping simple and attractive.

Key benefits include:

• Stylish curved front glass
• Integrated rear filtration
• Hidden equipment
• Powerful LED lighting
• Compact footprint
• Suitable for planted aquariums
• Beginner-friendly maintenance

Because the filter and lighting are built in, the Fluval Flex is ideal for hobbyists who want a clean, modern aquarium without lots of visible equipment.

Choosing Fish for a Fluval Flex Aquarium

Before choosing fish, consider the size of your aquarium.

Smaller Flex models are best suited to nano fish, shrimp, and carefully planned stocking. Larger models, such as the Fluval Flex 123L, provide more flexibility for community fish.

Important factors include:

• Adult fish size
• Temperament
• Swimming behaviour
• Group requirements
• Water temperature
• Filtration capacity
• Compatibility with plants and shrimp

Avoid choosing fish based only on how they look in the shop. Always consider their adult size and long-term care needs.

Best Fish for the Fluval Flex 34L

The Fluval Flex 34L is best suited to very small fish, shrimp, or a single feature fish.

Betta Fish

A Betta can make a beautiful centrepiece fish for a smaller Fluval Flex.

Benefits include:

• Stunning colour varieties
• Interesting personality
• Suitable for smaller aquariums
• Works well with gentle filtration

Bettas prefer calm water, so flow may need adjusting.

Chili Rasboras

Chili Rasboras are tiny, colourful schooling fish that suit nano aquariums.

They are:

• Peaceful
• Small
• Active
• Excellent in planted tanks

Keep them in groups for best behaviour.

Cherry Shrimp

Cherry Shrimp are ideal for planted Fluval Flex aquariums.

They help graze on algae and leftover food while adding colour and activity.

Best kept in mature, stable aquariums with plenty of plant cover.

Endler’s Livebearers

Endlers are colourful, active, and small.

They can work well in smaller aquariums, but they breed readily, so population control should be considered.

Best Fish for the Fluval Flex 57L

The 57L model gives more stocking flexibility while still remaining compact.

Ember Tetras

Ember Tetras are one of the best fish for planted Fluval Flex aquariums.

They are:

• Small
• Peaceful
• Bright orange
• Excellent in groups

They look especially striking against green plants.

Harlequin Rasboras

Harlequin Rasboras are hardy, peaceful, and excellent for beginners.

They prefer being kept in groups and work well in community aquariums.

Celestial Pearl Danios

Celestial Pearl Danios are beautiful nano fish with spotted bodies and colourful fins.

They suit planted aquariums with plenty of hiding places.

Pygmy Corydoras

Pygmy Corydoras are small, peaceful catfish that add activity to the lower levels of the tank.

They should be kept in groups and appreciate soft substrate.

Honey Gourami

A single Honey Gourami can make an excellent centrepiece fish in a peaceful Fluval Flex community.

They are calmer than many other gourami species and look fantastic in planted displays.

Best Fish for the Fluval Flex 123L

The larger Fluval Flex 123L allows for a more complete community aquarium.

Neon Tetras

Neon Tetras remain one of the most popular freshwater aquarium fish.

They are:

• Colourful
• Peaceful
• Ideal for planted tanks
• Best kept in groups

Their blue and red colours stand out beautifully under Fluval LED lighting.

Cardinal Tetras

Cardinal Tetras are similar to Neon Tetras but often appear more vibrant.

They do best in established aquariums with stable water conditions.

Corydoras Catfish

Corydoras are excellent bottom-dwelling community fish.

Popular species include:

• Bronze Corydoras
• Panda Corydoras
• Sterbai Corydoras

They should be kept in groups and benefit from sand or smooth substrate.

Cherry Barbs

Cherry Barbs are hardy, colourful, and peaceful.

They add activity without becoming aggressive and work well in planted community aquariums.

Dwarf Rainbowfish

Dwarf Rainbowfish are active, colourful fish suited to larger Flex setups.

They appreciate swimming space and good water quality.

Bristlenose Pleco

A Bristlenose Pleco can be suitable for the Fluval Flex 123L.

They help graze algae and have plenty of personality, but they still produce waste and require good filtration.

Fish to Avoid in Fluval Flex Aquariums

Some fish are commonly sold but are not ideal for smaller all-in-one aquariums.

Avoid:

• Common Plecos
• Goldfish in smaller Flex models
• Large cichlids
• Tiger Barbs in small communities
• Silver Sharks
• Clown Loaches
• Arowanas

These species either grow too large, require more swimming space, or may become unsuitable for peaceful community setups.

Best Plants for Fluval Flex Aquariums

The Fluval Flex lighting is well suited to many beginner and intermediate aquarium plants.

Plants improve the aquarium by:

• Providing shelter
• Reducing stress
• Competing with algae
• Improving water quality
• Creating a natural appearance

Choosing easy plants is the best way to start.

Java Fern

Java Fern is one of the easiest aquarium plants available.

Benefits include:

• Low maintenance
• Hardy
• Does not need planting in substrate
• Suitable for beginners

Attach it to wood or rock rather than burying the rhizome.

Anubias

Anubias is another excellent beginner plant.

It grows slowly and tolerates a wide range of conditions.

Best placement:

• Attached to wood
• Attached to rock
• Shaded areas

Like Java Fern, its rhizome should not be buried.

Cryptocoryne

Cryptocoryne plants are excellent for the foreground and midground.

They provide natural cover and come in several colours and leaf shapes.

Popular varieties include:

• Cryptocoryne wendtii
• Cryptocoryne beckettii
• Cryptocoryne parva

They may melt after planting but usually recover once established.

Amazon Sword

Amazon Sword plants make excellent background features in larger Fluval Flex aquariums.

They can grow large, so they are best suited to the 57L and 123L models.

They benefit from root tabs and nutrient-rich substrate.

Vallisneria

Vallisneria is a great background plant that creates tall, flowing leaves.

It works well in larger Flex aquariums and provides excellent cover for fish.

Java Moss

Java Moss is ideal for shrimp tanks and natural aquascapes.

It can be attached to:

• Wood
• Rocks
• Mesh
• Decorations

It provides excellent grazing areas for shrimp and fry.

Bucephalandra

Bucephalandra is a slow-growing plant that looks stunning in premium aquascapes.

It is ideal for attaching to hardscape and works well in smaller aquariums.

Floating Plants

Floating plants can help diffuse light and provide cover.

Good options include:

• Salvinia
• Frogbit
• Red Root Floaters

However, they should be managed carefully so they do not block too much light from plants below.

Best Aquascaping Ideas for Fluval Flex Tanks

The curved front glass of the Fluval Flex creates a strong visual effect, so simple layouts often work best.

Nature Aquarium Style

Use:

• Driftwood
• Rocks
• Java Fern
• Anubias
• Cryptocoryne

This creates a natural, low-maintenance display.

Shrimp Aquascape

Use:

• Moss
• Fine plants
• Small wood pieces
• Leaf litter

Ideal for Cherry Shrimp or Amano Shrimp.

Community Planted Tank

Use:

• Background stems
• Midground crypts
• Foreground mosses
• Schooling fish

This is perfect for the Fluval Flex 57L or 123L.

Example Stocking Ideas

Fluval Flex 34L

Option 1:

• 1 Betta
• Cherry Shrimp, if compatible
• Nerite Snail

Option 2:

• Small group of Chili Rasboras
• Cherry Shrimp
• Java Moss and Anubias

Fluval Flex 57L

Option 1:

• Ember Tetras
• Pygmy Corydoras
• Cherry Shrimp

Option 2:

• Harlequin Rasboras
• Honey Gourami
• Nerite Snails

Fluval Flex 123L

Option 1:

• Neon Tetras
• Corydoras
• Honey Gourami
• Bristlenose Pleco

Option 2:

• Cardinal Tetras
• Cherry Barbs
• Dwarf Rainbowfish
• Amano Shrimp

Always stock gradually and monitor water quality.

Maintenance Tips for a Healthy Fluval Flex

A good stocking and planting plan only works with regular maintenance.

Weekly tasks include:

• 20–30% water change
• Glass cleaning
• Water testing
• Removing dead plant leaves
• Checking filter flow

Monthly tasks include:

• Rinsing filter sponges in aquarium water
• Inspecting the return pump
• Trimming plants
• Replacing chemical media if used

Avoid replacing all filter media at once, as this can disrupt beneficial bacteria.

Common Mistakes to Avoid

Overstocking

Small aquariums have limited biological capacity.

Choosing Fish That Grow Too Large

Always research adult size.

Ignoring Group Requirements

Many nano fish need groups to feel secure.

Planting Rhizome Plants Incorrectly

Java Fern and Anubias should be attached to hardscape, not buried.

Overfeeding

Excess food quickly affects water quality.

Final Thoughts

The Fluval Flex is a fantastic aquarium range for creating stylish, planted freshwater displays. With the right fish and plants, it can become a thriving centrepiece that is easy to maintain and enjoyable to watch.

Smaller Fluval Flex models are best suited to nano fish, shrimp, or a single feature fish, while the larger 123L model offers more flexibility for peaceful community setups. Pairing suitable livestock with hardy plants such as Java Fern, Anubias, Cryptocoryne, Vallisneria, and Java Moss will give you the best chance of long-term success.

At Charterhouse Aquatics, we stock the full range of Fluval Flex aquariums, filter media, aquarium plants, substrates, aquascaping materials, fish foods, and maintenance products to help you create the perfect planted aquarium.