Klay said:According to pokemondb, Gligar doesn't learn Sand Tomb from Sandslash, but from Trapinch (and evos), Pineco (and evos) and Shuckle (for ingame poks) (http://pokemondb.net/pokedex/gligar/egg#move-sand-tomb)
For Cloyster, you can check it: http://pokemondb.net/pokedex/cloyster/egg
no idea what ~egg group is or means~Isguros said:Your Pokemon have to share a common egg group. It's like breeding a horse with a mouse: it won't work.
Klay said:The pokemon which has the move you want to teach needs to HAVE this move in its moveset. So, for Pineco, you need to teach it Sand Tomb by egg move (from Trapinch and evos, which learn Sand Tomb by leveling up) (http://pokemondb.net/pokedex/pineco/egg#move-sand-tomb)