A fish tank's substrate is one of the few decorating choices that also has a job to do - hold plants, host beneficial surface area, and not shift the water's chemistry while it's at it.

This is a Lemon Zest colourway of natural aquarium gravel, suitable for coldwater, tropical and saltwater set-ups. It doubles as a planting medium, and Pettex describe its increased surface area as improving anaerobic activity, while maintaining pH stability rather than altering it.

• Natural aquarium gravel, Lemon Zest colourway, sold as a 2kg bag
• Colour and size vary bag to bag, as it's a natural product
• Suitable for coldwater, tropical and saltwater set-ups
• Works as a planting medium; Pettex describe the increased surface area as improving anaerobic activity
• Maintains pH stability rather than altering it

On consistency. As with any natural gravel, expect some variation in stone size and shade between bags - Pettex don't publish a fixed grain size, so buy enough in one order if matching an existing tank closely matters to you.

Who it's for: fishkeepers who want a lighter, warmer-toned gravel for a coldwater, tropical or saltwater set-up, doubling as a planting substrate.