Fluval Flex 2.0 Aquarium Kit, Black - 57L

The Fluval Flex 2.0 Aquarium Kit, Black is the second-generation Flex at 57 litres, with a rebuilt filtration compartment, RGB and white LED lighting and a media stack that lifts out in one piece.

Key Features

• Measures 41.5 x 40 x 39 cm and holds 57 litres
• RGB plus white LED at 6500–7000K — the white channel is the one that grows plants and shows fish colours properly; the RGB is for effects
• Modular media stack: three interchangeable foam blocks and three biological or chemical baskets, so the filtration can be configured for the tank rather than the other way round
• EZ-Lift handle removes the whole media stack at once, which is the single biggest improvement over the original Flex
• Two eco-friendly Poly-Carb cartridges for mechanical and chemical filtration
• Dual output nozzles that adjust independently, plus an optional spray bar for gentle, even flow
• Hinged rear cover, a power cord channel, a feeding port and integrated cover risers for airflow
• Designated heater channel (heater sold separately)
• Made by Fluval, the aquatics brand of Rolf C. Hagen, which has been building aquarium filters since 1975

Setting It Up

• Put it where it will live before you add water. A full aquarium cannot be moved, and glass on an uneven surface cracks
• Check what the furniture underneath can take. Water weighs a kilo a litre before you add glass, gravel and rock
• A new tank has no bacteria in it. Cycling — running the filter for several weeks until it processes ammonia and nitrite to zero — has to happen before fish go in, or they sit in their own waste while the bacteria catch up
• Plant it and let it settle for a few weeks before the first fish. A tank that has been running a month is a far kinder place to arrive in
• Add fish a few at a time, not all at once

Living With It

• Lift the whole media stack out with the handle, service one block at a time and put it back
• Never wash biological media in tap water and never replace it all at once. Chlorine kills the bacteria living on it, and changing everything together restarts the cycle
• Fit the spray bar if you keep a betta, gouramis or a planted scape. The bare nozzles are too much current for those
• Set the light timer to around 8 hours. More light means more algae, not better plants
• Unplug anything electrical before putting your hands in the tank

Good To Know

• Stocking is the thing beginners get wrong. Ask what the fish grows into, not what it is in the shop — most tropicals sold at 2 cm do not stay that size
• Nothing in this kit heats the water unless stated. Tropical fish need a heater; a heater is sized at roughly 1 watt per litre
• A liquid test kit for ammonia, nitrite and nitrate tells you more about a tank than anything you can see
• Most tanks want 20–30% of the water changed weekly, with the replacement dechlorinated and matched for temperature
• The configurable media stack is the reason to choose the 2.0 over the original Flex. It makes servicing far less disruptive
• No heater included; a 57 L tropical tank needs roughly a 50 W heater
• Use a soft pad on the curved front glass, not a blade