i suggest you watch the ''14 months bichir growth'' video from ''bryan la '' i think its called on youtube he shows the growth on his endlicheris + lapradeis i think it was , very cool to watch and he also shows the very big difference from the sand in the tank he had them in white sand = no markings , fully black sands = fully black bichirs , i think the best sand for markings is beige/brownish/red ISH color sand