3rd gym ground type effectiveness

[xenu 1]

I'm currently challenging the 3rd gym with a marshtomp. I use mud bomb on the skuntank and the croagunk but the move is only 1x effective for some reason. This allows skuntank to get off 2 acid sprays which then lowers my special defense to hell. Pls help

[Candy 1688]

38 minutes ago, xenu said:

I'm currently challenging the 3rd gym with a marshtomp. I use mud bomb on the skuntank and the croagunk but the move is only 1x effective for some reason. This allows skuntank to get off 2 acid sprays which then lowers my special defense to hell. Pls help

If you're battling on Corrosive Field, Mud Bomb gains an additional Poison typing, which makes it 1X effective against Corey's poison types.

If you have a physical attacker, giving it a Telluric Seed will increase attack and set up baneful bunker which gives you one free damage turn, so it might be used as part of a strategy

[Autumn Zephyr 434]

It would seem that you are playing in the Corrosive Field version of the battle, which explains your problem: Mud Bomb becomes a Ground/Poison attack, and those pokemons' resistance to Poison neutralizes their weakness to Ground. Mud Slap and Mud Shot have the same effect, so those don't make viable substitutes.

 

Edit: Accelgor'd by Candy. Sugar rush, much? 

[Yahen 108]

Does corey's field poisons even non grounded mons?

[Autumn Zephyr 434]

33 minutes ago, Yahen said:

Does corey's field poisons even non grounded mons?

This is the Field Effect with the built-in Entry Hazard (basically, a Poison Typed Stealth Rock that only hits grounded pokemon). If it were the Corrosive Mist one, it would be able to Poison anything capable of getting the Status Effect.