Sand would be easier than clay. That way you arent trying to scrape it out; you can simply use a relatively high pressure water stream to flush all the sand out.
Species being kept:
Solenopsis "plebeius", Camponotus maritimus, Formica cf. subaenescens, Formica cf. aerata, Lasius cf. americanus, Lasius aphidicola, Lasius brevicornis, Lasius nr claviger, Nylanderia vividula, Temnothorax nevadensis, Temnothorax chandleri, Temnothorax arboreus Solenopsis validiuscula, Solenopsis truncorum, Solenopsis xyloni, Formica perpilosa, Formica cf. lasiodes, Formica cf. neogagates Pogonomyrmex californicus, Pogonomyrmex salinus, and Myrmecocystus testaceus!!!!
Hoping to find this year:
Myrmecocystus, Liometopum occidentale, Camponotus essigi, Camponotus fragilis, Manica bradleyi, Formica perpilosa, Pheidole hyatti, and a Parasitic Formica sp.
People are stupid. It explains a lot...