Route 212 with the poke Radar
Go into Pokemon mansion which is found on cinnibar island once inside wait until a wild Pokemon appears. Grimer is not that rare to find but you can find it.
In the Platinum it is 44, but I am not sure about Heartgold and Soulsilver.
No you find it in Pokemon mansion.
By evolving Grimer
Whit forest
You can find grimer on route 17 in Pokemon heartgold.route 16,route 17,route18,Celadon city and the safari zone.Good luck! :)
IN the Pokemon mansion you can find, ratatta, kofing, Picachu, grimer, and if your lucky, you will be able to find, Muck
You find Grimer in the Fiery Path. They are rare is it may seem that they are not there but they are. Its worth the time getting Grimer then evolving it to Muk, because Muk is probably one of the stronger Poison type Pokemon that are in Emerald!
Yes, Grimer can be caught in Pokemon Fire Red.
Grimer does not have a pre-evolution. The Pokemon before Grimer in the PokeDex is Dewgong, evolution of Seel.
in route 212 hope this helps
you can catch grimer in celadon city by either fishing or surfing. it says so on Serebii.net