Here is a real simple way to use .htaccess to redirect your forum member pages to a custom member page, that may not be the default EE member account page under /member.
Note: If you have removed index.php using .htaccess, place this before your rewrite rule.
In your .htaccess add the following code:
# Redirect /forum/member/ to /account/public
Redirect /forum/member/ http://example.com/account/public/
And your done! Now, wasnt that easy?