Conventional wisdom is no, it won't work with Viejas. I think it wmay work if there are no femalees in the tank and you raise them together. I have kept adult Bifa, Maculicauda, and Syn males together with few problems, until a syn started mating with a female Carpinitis which prompted brutal fighting. Once I gave away the female Carpinits (replaced with a male), the fighting stopped. Either way you may get some bad fighting, or you may get lucky and have peace, but mixing sexes almost guaruntees eventual death.