Fluval Flex 15 Gallon Review

If you want to start a community tank or give your betta more room to explore, then 15-gallon tanks are a great choice. They’re big enough to give you a lot of different options, but not too big that they won’t fit anywhere. After reading this Fluval flex 15 gallon review you’ll be ready to purchase a great tank that will leave you happy for years!

What Does The Fluval Flex Come With?

The Fluval flex isn’t just an aquarium on its own. It’s a kit that’s going to come with a lot of the equipment you’ll need to get your tank started. Here’s everything that’s going to come with your purchase:
  • A 3 stage filtration system. The filter system that comes with this tank has an oversized mechanical, biological and chemical media, which is going to help your water look crystal clear.
  • An LED light system with color control and special effects including cloud cover and lightning.
  • The tank itself which measures 16″ x 15″ x 15″ (W x D x H).
While the fluval flex aquarium kit does come with a lot of great features, it is going to be up to you to buy the rest. Along with what’s given to you, you’ll definitely need a heater, food and water conditioner. On top of this, while they’re not completely necessary it’s also strongly recommended that you buy substrate, plants and aquarium decorations as well.

Fluval Flex 15 Gallon Review (The Components)

For an in-depth Fluval flex 15 gallon review, I’m going to break the review down to the separate components of the tank. This part will consist of reviewing the tank, lights, and filter that come with the tank.

The Tank

First of all, the tank. This is one of the biggest reasons people buy aquarium kits and it’s the one that often drives the most attention. You’ll notice right away that the Fluval flex 15 gallon is very unique. Here are some of the best features of the tank, as well as some things that you’re going to need to be aware of.


  • One of the best benefits to this tank is the compartment in the back. It gives you enough space to hide all the equipment that you don’t want to be seen in the front of your tank. This includes the filter, heater and any cords. When you do this, your tank has a more natural feel, and you don’t have to worry about any of your equipment damaging your bettas fins.
  • The grid pattern around the top of the tank is also a nice touch. It helps hide any water stains from the outside. This means your tank looks a lot cleaner.
  • The design of the tank lets you see your betta from angles that a normal tank wouldn’t.


  • One of the biggest problems that come with the tank is the size of the compartment for your filter. Because it’s cut off and allows you to hide all your equipment it means you lose space in your tank. So while the tank states that it’s 15 gallons, in all honesty, you’re only going to get about 12/13 gallons of swim space and 2/3 gallons of water your fish can’t get too. However, while on the surface this may seem bad, it means that you’ll never overstock your aquarium.
  • This is down to personal preference, but some people don’t like the black background of the tank. If you wanted to you can just leave it, but you can also use an aquarium wallpaper to cover up the back of the tank and make it look a bit nicer.

The Lighting System

Next up is the lighting system. As mentioned earlier it’s a lot more interesting than other lighting systems and it’s definitely something you should take into consideration when buying this tank.


  • One of the biggest benefits of the light is that it supports plant growth. If you’re looking to have live plants in your tank that need low to medium light to grow then it will definitely do the trick. If you’re a beginner you may not need to worry about it so much, but when you get more experienced it’s definitely something you’re going to be looking for.
  • The light is also going to show off your betta’s color a lot better!
  • It comes with 15 different colors for you to choose from as well as a variety of different special effect lighting. There’s also a specific effect that allows you to slowly cycle through all the different colors.


  • One of the biggest cons of this lighting system is that you can’t grow high light plants. If your main goal of the tank isn’t to grow plants, then it’s not going to be a problem. But later on down the line, you may need to swap the lights out for something stronger. (However, people have reported using submersible suction cup lights to improve the lighting in their tank in cases where they have plants that need more lighting.)

Filtration System

And, lastly, one of the most important aspects of any tank, the filtration system. If you don’t have a good filtration system then your betta and any other fish in your tank are going to suffer. You’ll be pleased to know that the filter that comes with the Fluval flex 15 is exceptional and you won’t have to worry about it not cleaning the tank properly.


  • The filter is powerful, and because of the oversized media, it’s going to work even better than normal filters.
  • Because of the space in the back of the tank, you can add even more filter cartridges if you want. My two recommendations would be a water polisher or another bacterial filter.
  • The sleek design of the filter is also a nice touch, and once again there’s enough space in the back with the filter for other aquarium equipment.


  • One problem that a few people have noticed is the size of the slits. If you have smaller fish in the tank then they may end up getting sucked into the filter. While this won’t be a problem for your betta, it can be for other fish. Especially if you’re keeping your betta with live bearing fish such as platies. You may find that a lot of their fry end up in the filtration system.
  • If you don’t clean the filter enough then it can easily become too dirty. When this happens you’ll notice that the current coming from the filter is a lot weaker and it may cause the tank to become less oxygenated.

Who Is This Aquarium For?

This is a nice little kit, and before you plan on buying it you should make sure that it’s really for you. If you’re any of the things listed below then you should definitely consider buying it.
  • A betta owner who wants to start a community tank.
  • Someone who is interested in keeping live plants with their betta.
  • Someone who wants to give their betta extra space to swim and enjoy.
If you feel like you’re one or more of the above then you should definitely get the Fluval Flex 15 gallon it a great choice for your needs.

What Are Other Customers On Amazon Saying?

On top of this Fluval flex 15-gallon review, there are also a lot of people on Amazon who have purchased this tank and enjoyed it! Here are a few of the reviews left by them:
  • “Overall I love this tank and couldn’t be happier with it.”
  • “LOVE THIS AQUARIUM. Looks absolutely amazing, packaging was great, no cracks or damage. “
  • “Had This Tank For Two Weeks Now And Have Seen Plant Growth Everywhere. The Shrimp & Plants Love It & You Really Can’t Ask For More.”
  • “Beautiful design and I love all the different light-effects that come with a remote control. Nice that there’s also a private compartment to keep the wired components of the tank out of sight.”
  • “I was pleasantly surprised by the size and quality. I would buy this again. Had for a few months and is working great and the front curve makes it appear bigger than it is. “

Fluval Flex 15 Gallon – Recap

The fluval felx 15 gallon is a great tank for beginners and more experienced fish keepers alike. Here’s a quick recap of the main perks of the tank, as well as things to be mindful about.
  • You’re not just going to be getting a tank. You’re also going to be getting an LED lighting system that supports plant growth and has multiple settings. And on top of this you’ll also get a 3 stage filtration system.
  • One of biggest perks of the tank itself is the fact that you can hide all of the equipment needed in a compartment in the back.
  • However, that compartment does take space out of the tank your betta can’t swim in.
  • The lighting system that comes with the tank comes with 15 different color settings as well as special effects.
  • The filter is solid and comes with three oversized media cartridges. However, there’s also room in the back for you to add more if you’d like.
  • One of the biggest downsides of the filter is that if you have fish in your tank which are too small, then they may be able to swim into it.
If you’re looking for a tank to get started at a reasonable price then you should definitely buy the Fluval Flex 15 Gallon! If you think it’s too big for your needs then why not check out the best 10-gallon tanks on the market right now! OR likewise, if you’re looking for a tank that’s a little bigger then check out the best 20 gallons tanks you can buy!
About the author

Hey there! I'm Antonio, the passionate owner and chief editor of Betta Care Fish Guide. With over half a decade of hands-on experience, I've become your go-to expert for all things betta and tropical fish.

Over the past 5 years, I've not only kept bettas and other tropical fish but also connected with a diverse network of hobbyists, seasoned fishkeepers, and even veterinarians.

Now, I want to help other beginner fish keepers who had the same questions as me when they were just starting out! So they can save themselves a ton of time and keep their fish happy and healthy!

2 thoughts on “Fluval Flex 15 Gallon Review”

  1. Terrible tank that didnt even last me 2 years! Dangerous enough to crack and spill water all over the electrical chords and my floor in the middle of the night. I do not recommend it. I have photos to prove the front of this tank (which is curved) was made too fragile and thin, so all the water inside had its entire weight finally breaking the glass in an S shape.


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