Fluval Flex 9

Fluval Flex 9 is a 34 × 33 × 33 cm (13.4 × 13 × 13 in) aquarium, rated at 34 L (9 gal). Its footprint is 34 × 33 cm and the water stands about 27 cm deep once a 6 cm substrate layer is in — the two numbers that decide what you can plant in it and what you can stock it with.

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At a glance

Size34 × 33 × 33 cm (13.4 × 13 × 13 in)
Volume34 L (9 gal), as sold
Water after substrateAbout 28 L (7 gal) with a 6 cm substrate layer
Footprint34 × 33 cm (13.4 × 13 in)
Water depth27 cm (10.6 in)
Substrate neededAbout 7 L for a 6 cm layer

Before it goes in

  • Fluval Flex 9 is 34 × 33 × 33 cm (13.4 × 13 × 13 in) — rated at 34 L (9 gal), and roughly 28 L (7 gal) of actual water once a 6 cm substrate layer and the hardscape are in.
  • That layer takes about 7 L of substrate, which is what you order by.
  • 21 of the 160 animals in this library list a minimum tank at or under 34 L (9 gal). The biggest of them that still fit are Ember Tetra and Chili Rasbora. African Dwarf Frog and African Clawed Frog need more than this.
  • The water sits about 27 cm (10.6 in) deep over the substrate. Plants that get taller than that — Hygrophila corymbosa 'Siamensis' and Water Sprite — reach the surface and start growing along it, which is a look you either want or trim.
  • Its footprint is 34 × 33 cm, and that is the area a carpet has to cover — the number that decides how many pots you buy, not the volume.

What are its dimensions?

34 × 33 × 33 cm (13.4 × 13 × 13 in).

How much water does it hold?

It is sold as 34 L (9 gal), and roughly 28 L (7 gal) of actual water once the substrate is in. Stocking works off the second number; minimum-tank-size advice works off the first.

How much substrate does it take?

About 7 L for a 6 cm layer.

What fits in it?

21 of the 160 animals in this library list a minimum tank at or under its volume, and the water depth of about 27 cm sets which plants can grow without reaching the surface.

What fits in it

Often compared with

Fluval Flex 9Eheim Aquastyle 3560F Shallow
Size34 × 33 × 33 cm31 × 31 × 36 cm60 × 30 × 18 cm
Volume34 L35 L32 L
Footprint34 × 33 cm31 × 31 cm60 × 30 cm
Water depth27 cm30 cm12 cm

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