That thing that might be crawling in your tank should be dragonfly nymph. These are usually from the plants that you did not wash and quarantine before you put them in your shrimp tank.
Wrigglers might be mosquito larvae.
I might be wrong, just making a guess.
For dragonfly nymphs, you should manually remove them.
As for the wrigglers, you can try adding shrimp friendly fishes. Go search the forums for various shrimp safe fishes.
A picture of both would help us identify them for you accurately.
Regards,
Misery.
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