Gravel does more in a tank than sit there looking tidy — it's the surface bacteria colonise to keep the water itself in balance, which is why the grain matters as much as the colour blend on top of it.

This is a natural gravel in a blended-colour mix rather than a single dyed shade, so Pettex note some variation in colour and size is normal between bags. It's rated for coldwater, tropical and saltwater set-ups alike, works as a planting substrate, and the increased surface area is said to improve anaerobic activity and help maintain the tank's pH stability.

• Natural gravel, blended colour mix
• Suitable for coldwater, tropical and saltwater aquariums
• Works as a planting substrate
• Increased surface area for anaerobic activity
• Helps maintain pH stability
• 2kg or 8kg bag

One thing worth knowing. Being a natural product means some colour and grain-size variation between bags is normal rather than a fault, so if you're aiming for a very specific, even blend across a larger tank, mixing bags together as you go can help even it out.

Who it's for: aquarium keepers wanting a smaller 2kg top-up bag of natural blended gravel, for coldwater, tropical or saltwater tanks.