In a rainforest vivarium the substrate is not decoration, it is half the humidity system. Water has to come from somewhere between mistings, and a floor that holds moisture and releases it slowly does more for a tropical species than anything you can bolt to the glass. Get it wrong and you spend the rest of the year chasing a hygrometer.

This is orchid bark: natural bark, chosen by Pettex for moisture retention and aimed at rainforest and tropical species that need a high-humidity environment. It is heat treated to kill off micro organisms before it is bagged, and Pettex state their substrates are sourced from sustainable, renewable sources. It is sold by volume rather than weight — a 10 litre bag, which arrives as a 2.4kg parcel.

• 10 litre bag
• Made from natural bark, nothing else declared
• Chosen for moisture retention in high-humidity setups
• Heat treated and sanitised before bagging
• Listed for all snakes, tropical reptiles, invertebrates and amphibians
• 2.4kg parcel weight

Nothing here tells you the piece size. Pettex publish no chip dimensions, no guidance on how deep to lay it, and no note on which animals are too small to be safe around bark of whatever grade is in the bag. That matters, because loose chunky substrate and small mouths are a combination reptile keepers argue about, and feeding off a dish rather than off the floor is a conversation worth having with your exotics vet rather than with a bag label.

Who it's for: keepers of rainforest and tropical species — crested geckos, tree frogs, many snakes and invertebrates — who need a floor that holds humidity rather than one that just looks like a jungle.