How can I modify the md-input-container in angularJS

You could do something like .hide-validation-error .md-errors-spacer { display: none; }, and then you would just need to add the class hide-validation-error to any of the <md-input-container>'s that you know won't need validation.

use this css:

md-input-container:not(.md-input-invalid) .md-errors-spacer {
    display: none;
}