I am playing Heartgold and I want a grimer (because I hate weezing its still good) so I can have muk. On each route I check for new Pokemon. I finally found one, but it is really low-leveled because it is postgame in celadon city. Is there any way to get it in game?
You can find grimers on these routes: Route 16, Route 17, Route 18, Celadon City
Hope I helped! :D