Version 1.4.1 (don't know if this applies to other versions)

If you are allowing comments, but not user registration, such as you might with a password protected album while not having user registration, you may wish to have all comments automatically held for moderation.

Open file in text editor:
zp-extensions/functions.php

Line 843
change to
$commentobj->setInModeration(1);

Line 889
change to
$commentobj->setInModeration(1);

Or you could use select the "none" spam filter and set its action to "moderate" and thus not have to make a hack to the zenphoto core which surely will cause you problems in the long run.

Good to know, thank you.