Not sure if you need both caulurpa and cheato.
One school of thought in a sump is to put a few marine pure blocks in a chamber and replace one at a time as they start getting clogged (or crumble).
The idea is that all rock will eventually become clogged with detritus as well as serve as anchor spots for nuisance algae, so keep rock at a minimum in the DT and let the marine pure in the sump do the bulk of the nitrification.
If I had to do it all over again, I'd go that route.
Meanwhile, IME, the caulurpa eventually finds its way into the cheato and chokes out the cheato. Not the end of the world, and this is just my experience, but that I can't rid my fuge of the stuff and it quickly over takes my cheato used to bother me. Not just let them duke it out. I do notice the tigger pods prefer the cheato over the caulurpa.