Hi could anyone tell me if ground wallnut is ok to use for my leopard gecko if not what is best to use.
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Ground walnut is a poor choice for a leopard gecko substrate as are ALL particulate substrates due to an extremely high risk of impaction :-(.
Best choices are textured tiles: slate, ceramic, or porcelain. Paper towels can be used in a pinch till you find some tiles. Reptile carpet harbors bacteria from the feces and the urine.