I'm not sure or you can go back to the city reborn right now? Anyways, if you can't: some mons you can catch and use are:
-Polyswine (evolve it by teaching at the move relearner in the circus),
-Floatzel (i'd recommend this one for this gym!) (learnes ice fang, along side with an ice gem and his high speed he can probably 1HKO or 2 HKO after ultra potion the altaria)
- A rock stealth set up'er as said by someone before. I think geodude it he only possibility (with sturdy)?? IDK, maybe that sandblock pokemon which you "sleep" during the puzzle.