If you do both that will probably get rid of them all but the assassins need sand to burrow in.
sofar ive been lucky and never had such an issue. i dont know if i'll ever have a sand substrate. it sounds a bit tricky to use the gravel vac on sand.
Kigurumi (F) yellow PK 7/4/13, Kurama VT 9/8/13, Zeydalus Salamander EE PK 21/3/14, Ryuk turquoise dragon DeT 8/5/14----Crested Gecko (8ths old) Sven Cal 27/12/11,
RIP: Osiris copper DT, Nel blue VT, Nelliel turquoise grizzle DT, Zaku red cambo, Blitzkreig Pineapple CT, Halloween orange chocolate DeT, Grimmjow, turquoise green CT