Because the court immediately issues the automatic stay after receiving a compliant declaration of bankruptcy, the next paycheck should have all eligible garnishments removed. However, it can take some time for the notice to be received, so you may want to let your employer and the garnishing creditor know about the filing ahead of time to expedite the process.
This isn’t foolproof, however — if a creditor files a form to have the automatic stay lifted, or if you’ve filed for multiple bankruptcies, the garnishment may be permitted to continue.