I have been toying with the idea of acquiring a nice spearer, one of the funky types with the weird "flat panel" eyes and such. I could put just a little rock in the rear and a super deep sand bed for it to burrow in. But I've been posting to dr. caldwell the uber-stomatopod guy and am not certain how to recreate the correct substrate in an aquarium. In the wild, mantids that burrow (spearers) make their homes in just the right kind of substrate - when dug it supports the weight, it doesn't cave in. this is due to roots, detritus and debris, etc ... but in aquariums the substrate always caves in. i've experimented with making a few different substrate mixes with various commercial substrates and reef related products, but they all cave in too easily.