Fluval Foam Filter Block for Flex Aquarium Kit

The Fluval Foam Filter Block is the genuine replacement mechanical foam for the rear filter chamber of the larger Fluval Flex aquariums. As water passes through, the open-cell foam traps debris, uneaten food, and waste before they cloud your tank, keeping the water clear and protecting the biological media behind it. Keep a spare on hand so a routine swap is quick and mess-free. Browse our filter media and cartridges for the rest of your maintenance kit.

Features

• Genuine Fluval replacement foam block
• Open-cell foam traps large and fine particles for mechanical filtration
• Protects biological and chemical media and keeps flow strong
• Rinse in tank water to reuse; replace when it starts to break down
• Safe for freshwater and saltwater aquariums

Compatibility

• Fluval Flex, 15 US gal / 57 L
• Fluval Flex, 32.5 US gal / 123 L

For the smaller Flex 9 gallon, Spec, Evo, and Betta kits, use the Fluval Foam Filter Block for those nano kits.

Specifications

Recommended Pairings

• Fluval Flex 32.5 Aquarium Kit — the aquarium this foam block keeps running clean.
• Fluval Foam Filter Block for nano kits — the matching foam for Spec, Evo, Flex 9, and Betta.
• Water care and conditioners — keep spare media and treatments stocked.

Frequently Asked Questions

How often should I replace the foam? Rinse it in old tank water at each water change to clear trapped debris, and replace it when it starts to fall apart or no longer springs back, usually every few months.

Should I replace all my media at once? No. Swap the foam separately from your biological media so you never remove all your beneficial bacteria at the same time.

Which Flex does this fit? This block fits the Fluval Flex 15 gallon and Flex 32.5 gallon aquariums. For the Flex 9 gallon or the Spec, Evo, and Betta kits, use the nano foam block.

Can I use it in saltwater? Yes. The foam is inert and works in both freshwater and marine setups.