If you get a bolt with a flat nock, can you later replace it with a half-moon nock, or vice-versa?

Or does that depend on the manufacturer?

I guess that the answer is "yes".

Yes. You should be able to use an arrow puller to remove the nock. All the ones I've ever seen are simply pushed in.

Carbon Express bolts come with both flat nocks and moon nocks.

ETA: Just realized you said aluminum. I don't know if that changes things. I don't see why it would though.

Thanks...

I had ordered bolts with flat nocks, realized my error, and cancelled the order. That vendor did not have those bolts with the other style nocks, but I found the ones that I needed on Amazon and ordered those.

I did see some YouTube videos on the subject, and did not realize prior to that that the bolts were hollow all the way through the shaft (I'm new to archery, obviously).