Some kind of worm?

Either bloodworm or planaria, which doesn't matter if you have fish.

Which is to say, worms and planaria makes a great food for you fish.

If its a shrimp only tank though, they wont hurt the shrimp, but the shrimp wont eat them, and they will build up if you are overfeeding. There are shrimp safe products to get rid of them, but I've never used those and dont know too much about them other then that they exist. Frequent water changes and thorough gravel vacuuming will also cut their numbers. Personally, I just ignore them, and even enjoy them a bit. But thats probably just a holdover from my saltwater days and looking for any moving thing in the live rock.

Also I see you're from Calgary. How did the stampede treat you? I meant to go this year but things got in the way. Facebook photos from friends made it look like I missed out.

Don't worry my friend! It's just a small worm dat u can see inside d tank. Yeah it do come when u plant and keep fishes. Believe me it will not harm at all. In fact if d water is not kept clean it will die very soon. U really need to take care of d tank.

You didn't miss to much just a bunch a drunk people partying for two weeks ha. It's crazy here for two weeks.