i have a dahli ring loach that loves to bury himself, its amazing how fast he is, one second hes above ground the next minute hes gone, occasionally you see 2 eyes sticking out, most loaches will usually bury, my red finned blue loach burys his head in the gravel leaving his tail sticking out vertical thinking that no one can see him, btw i have gravel in the tanks with my loaches but they dig more in the ones with small grain, in sand they should be happy