On the mailing list of my fish supplier I saw he offered Sprot (Dutch for Sprat), frozen, per kilo, for 8 euro.
These fish are 9 to 12/13 cm long (and sometimes a few centimeters larger). They seemed to me the perfect size for the larger Thamnophis species, like the females of T. eques scotti and T. s. tetrataenia. So I ordered one bag together with some bags of smelt and some blisters of Dillies. Just to give it a try.
On this site Thiaminase - The Free Freshwater and Saltwater Aquarium Encyclopedia Anyone Can Edit - The Aquarium Wiki and this one Thiaminase (Chemicals Summary) mention that Sprattus sprattus does not contain Thiaminase.
Well, on the pictures you can see if they liked this new food item...