Did my orchid seedling get munched on?

[UsagiGreenPaw]

There's two roots in the picture I want to verify have munch marks.

I finally got my fungus gnat problem under control about a month ago and I haven't seen a single one for weeks. In the last few days I suddenly saw 3 or 4. They were all killed and I put out traps to catch any I didnt see.

When watering today I noticed the root on the left towards the surface has a hole in it near the tip. Then I dug a little deeper to try and find the little villain and havent seen it, excep I found another root with the same damage on the right farther down.

Looks like gnat larvae snacking, yes?

[UsagiGreenPaw]

Ah! Found the little thing! It's a slug! I emptied the pot and sifted through all the medium and it's a little slimer.
I have no idea where it came from. I'm guessing in a recent plant purchase.

Do i need to do anything like treat all my plants if I find a single little slug? Is there likely more? Throw out old medium, I'm guessing. I dont have any small bark right now, so maybe I'll place it in a bit of sphagnum moss until i get some fine bark this week.
Found another eaten root. So ticked off it ate the best roots. Of course it did.

[estación seca]

Slugs are a big problem. You can remove all the medium, then soak the plant in water for a few hours. Any slugs should come to the surface. The eggs don't, however.