A filter that's too powerful for a small tank creates a current strong enough to exhaust smaller fish, which is why matching flow rate to tank size matters more than just buying the biggest filter available.

Fluval's Mini filter runs at 200 litres per hour and is built for aquariums up to 45 litres, drawing 5W. Fluval describe it as simple, quiet and efficient, suited to smaller coldwater or tropical setups.

• 200 litres per hour flow rate
• For aquariums up to 45 litres
• 5W power draw
• Suitable for coldwater or tropical tanks

On maintenance. Fluval don't publish a filter media replacement schedule or a servicing interval for this model on the facts we have, so check the unit itself for guidance rather than assuming it runs indefinitely without attention.

Who it's for: owners of a small aquarium, up to 45 litres, who want a straightforward filter rather than an oversized one built for a much bigger tank.