How to disable GELI selectively?

[thor]

Hello!

Here I have a computer with 2 HDDs partitioned identically with GELI 
encrypted root as in 
https://forums.freebsd.org/threads/howto-full-disk-encryption-fast-way.19082/

When I boot the computer it properly asks the passphrase for /dev/ada0p3 
and mounts /dev/ada0p3.eli as a root.

Then, it asks "Enter passphrase for gptid...." which I don't want since 
the second HDD should be attached manually when needed ONLY and all 
other time it should be unmounted. I am to press enter enough times to 
make me mad.

I have found 
https://lists.freebsd.org/pipermail/freebsd-stable/2012-July/068704.html 
but it resolves the problem how to mount /dev/ada1p3.eli on boot but not 
how not to mount it.

kern.geom.eli.tries=0 makes geli not to ask for every passphrase 
including /dev/ada0p3 and the boot correspondingly totally fails.

What should I do?

Thor