Fluval Flex 57L Aquarium, the Perfect Choice of 2020!

fluval flex 57l aquarium review

Fluval Flex 57L is a popular choice among fishkeepers. If you are a newbie, this 15-gallon aquarium offers some exciting features for your jumpstart! This size is spacious enough to build it as your first community tank.

This Fluval Flex aquarium can be an excellent choice as a planted tank, and you can have live plants along with decors to match your preference. Fluval Flex comes up with some distinctive features that make the product attractive to the users.

The curved front of the tank is stylish looking, and a handy lighting system visually appeals. Brilliant illumination is the focused feature of this aquarium. Not only the outlook but also useful aquarium features combining altogether make a complete package for the aquarists. If you are looking for your first ever tank to start fishkeeping, the Fluval Flex 57L will not disappoint you.

Fluval Flex 57L Aquarium Review

Fantastic features of Fluval Flex 57L

Smart lighting: 

Fluval Flex 57L fish tank comes up with 2450 lux LEDs capable of creating a shimmering effect and an innumerable number of color combinations. Simultaneously, the 7500K LED lamp is producing a complete spectrum that can promote live plant growth. 

An essential consideration of a lighting unit is how comfortably you can control it. This product features a super easy FLEXPad remote control. You can choose from an enormous number of color blending and special effects as per your likings. The infrared remote sensor is enough sensitive and easy access through the transparent glass aquarium, makes the control communication smooth. 

Three-stage filtration system:

While you are an aquarist, you’ll find the main challenge is to maintain the aquarium environment healthy, specifically ensuring the water quality. Therefore, an effective filtration system is crucial. The Fluval Flex 57L aquarium includes a three-stage filtration system. Three water purification stages are mechanical, chemical, and biological filtration, with foam, carbon, and BioMax as filter media. 

A multidirectional dual output feature will give you the option to customize the water flow. Flow customization option is useful, especially if you keep Betta fish or live plants like Frogbit or Duckweed in your aquarium because these inhabitants are not comfortable with high water flow. 

Filtration units are essential but not visually pleasing. So in Fluval Flex 57L Aquarium, the entire filtration system is hidden in a rear compartment. Stylish honeycomb mask conceals the filtration unit without hampering its primary function.  

Sleek and elegant outlook:

The curved front can create an illumination of a broader view of an underwater world. Pretty lighting with appropriate décors can take the beauty of this aquarium on a whole new level. You will love to see your aquatic pets are swimming, relaxing, and playing in a nicely decorated home for them.

Product Specification

Dimensions: 16 x 15 x 15″ (41 x 39 x 39 cm)

Capacity: 15 US Gal (57 L)

Wattage: 10.8 Watt

Lumens: 2450 lm

Color Temp. 7500K

Pump Output: 132 US Gal/h (500 L/h)

fluval flex 57l box

Pros and Cons


  • Perfect lighting spectrum for plant growth
  • FLEXPad remote control is super easy to control
  • An enormous number of color blending option
  • A three-stage filtration system ensures water quality
  • Hidden filtration system allows a better view of the aquarium
  • Curved front is stylish and creates an illusion of a more extensive view
  • The top cover opening allows easy feeding
  • Two years limited warranty


  • Only for freshwater use
  • Glass aquariums are fragile prone to cracking if not carefully handled
  • The flow nozzles are on the same side as the feeding hole, that can blast the food around

When Fluval Flex 57L is a perfect match for you

To start a community tank

Some people prefer having various kinds of fish, making a perfect combination. For making such a community tank, you have to ensure sufficient space with versatile features. In Fluval Flex 57L, you will get all of these. A 15-gallon aquarium is spacious enough. It has the multidirectional dual output for customized flow that allows a favorable flow for different kinds of fish. A proper selection of substrate, along with the available features, can make this one an ideal community tank.

A perfect Betta fish tank

The customized flow option makes this tank ideal for Betta, as they are comfortable with low water flow. Betta fish struggles if the flow output is very high, which will not happen in Fluval Flex. A suitable heater to maintain warmer surroundings will build this tank a perfect home for Betta.

Ideal for a planted aquarium

The lighting system is the best feature for Fluval Flex, with so many variations that make it a perfect aquarium for keeping live plants. You can adjust the illumination from very high to low, just as much as your plant require. On the other hand, if you keep floating plants, a high flow pump is not suitable for them. But in Fluval Flex, you can customize the flow output.

For a beginner

The Fluval Flex 57L is straightforward to start and maintain. If you are planning to have your very first aquarium and you have a moderate budget, pick it without hesitation. This quality product is definitely going to make your first fishkeeping experience a pleasurable one.


Does the Fluval Flex 57L come with a heater?

Fluval Flex Comes with so many useful features, but the rest you have to buy additionally. It does not come with a heater, while the heater is an essential item for an aquarium, and you cannot do without it. So definitely you have to buy a suitable aquarium heater, decors and other accessories like a water conditioner.

What will be the best heater for Fluval Flex 57L?

In a simple rule of thumb, while selecting a heater, the bare minimum watt you need is 2.5 times the tank volume. That means for a 15-gallon tank, a 37.5-watt heater is a minimum requirement, but remember, the ambient temperature plays a vital role here. If you live in a too cold place, where the required temperature rise of water is 10 degrees Fahrenheit, for say, you will need a 150-watt heater. So choose between 50 to 150 watts. To make the searching process more relaxed, you can take a peek at our picks of the best aquarium heaters

Can I use it as a planted aquarium? What type of plants would be better for it?

Lighting is the focused feature for Fluval Flex 57L fish tank and has sufficient lighting options to grow live plants. The lighting unit of this product allows you to adjust the light for bright to low settings, so any kind of freshwater plant (high, medium, or low light) is suitable to grow in this tank.  

Is the filter an under-gravel filter?

The filter remains hidden in a rear compartment, and a stylish honeycomb wrap conceals the entire filtration unit. Still, it is not an under gravel filter. The circulating pump sucks water through two intake vents, one at the upper left and another at the lower left.

How many fish are in Fluval Flex 57L?

There is a thumb rule for rough estimation that is one inch per gallon. That means in a 15-gallon tank, you can keep fish with a total of 15 inches of length. ( For example, three fish of five inches length) But this is only a gross estimation considering the worst-case scenario of filtration capacity. But in a 10-gallon tank with an effective filtration system, a combination of 6 to 8 small and medium fish is quite perfect for keeping.

Unboxing and setup Fluval Flex - video tutorial


Fluval is a renowned name in the fishkeeping arena. Over 20 years, they are providing many useful good-quality fishkeeping items. In our honest opinion, Fluval Flex 57L is one of the best aquariums of 2020 to start with, especially if you want to have live plants. 

The compact design of the Fluval Flex 57L aquarium makes it easier to place in any room with limited space. The pump is quiet enough that you can put it in your bedroom also. This elegant looking fish tank will decorate any room perfectly.   

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Sujit Modak Aquarium Tales Owner
Sujit Modak

Hello, everyone! Welcome to my aquarium blog. Fishkeeping is my passion, and I started this fascinating hobby back in 2006. Besides my engineering profession, I deeply studied many fishkeeping topics since I started building my home aquarium. I researched effective aquarium filtration and lighting of planted aquariums. I am keeping 20+ species of freshwater and saltwater fish as my aquatic pet collection. I successfully experimented with a complex ecosystem inside the aquarium, biotope aquariums, aquaponics, etc. I would love to share some learnings from my hands-on experience of the last 14 years. Hopefully, my sharing will be somewhat helpful to make your aquarium journey awesome! 

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