Question about Reef Dynamic reactor (mod)

[hrdneglcry]

I have a Reef Dynamic reactor that is incomplete. It is mostly complete but it is missing the top and some of the plumbing. I can probably plumb it but I not sure how to cap the top. The collar has three nubs and no threads. Any tips on how to cap the top? Two pics, one of mine with no cap and one of a complete reactor.

 

[blaxsun]

I'd just buy a new reactor (you can get them reasonably cheap from BRS).