show menu if tag

I hope this is possible. I want to show a certain menu only when there is a certain tag. Is that even possible?

This is what I figured out so far: `<?php

$posttags = get_the_tags();
if ($posttags) {
foreach($posttags as $tag) {
if ($tag->name == “mycustomtag” ) {

wp_nav_menu( array( ‘theme_location’ => ‘secondary’, ‘container’ => ‘dropdown clearfix’, ‘menu_class’ => ‘nav nav-stacked’, ‘menu_id’ => ‘side’));

} else {

wp_nav_menu( array( ‘theme_location’ => ‘primary’, ‘container’ => ‘dropdown clearfix’, ‘menu_class’ => ‘nav nav-stacked’, ‘menu_id’ => ‘side’));

}
}}
?>`

As it is a menu, it’s outside the loop.

If I simply put

<?php if (is_tag('mycustomtag')) : ?>

it shows correctly on archive pages but not on other pages.

Thanks!