You cant match query string using RewriteRule
. Use it like this:
RewriteEngine On
RewriteCond %{QUERY_STRING} ^f=65&t=6$
RewriteRule ^forum/viewtopic\.php$ /page/name-of-the-page? [R=301,L]
RewriteCond %{QUERY_STRING} ^f=30&t=5$
RewriteRule ^forum/viewtopic\.php$ /page/another-name-of-the-page? [R=301,L]
?
in the end is used to strip-off any existing query string.