I always administer fenbendazole at 100 mg/kg, I've never even heard of anyone using a dose as low as 25 for snakes before

I adminster it via tube or injecting it in to the feeder once, and then again in 2 weeks. It would still be a good idea to get a fecal done since fenbendazole may not eliminate ALL the parasites/protozoa that that snake may be harbouring, although you wouldn't need to get a fecal done in order to treat the snake with fenbendazole.