I never dosed anything into my tank other than kalkwaser. Sounds interesting, almost like some tanks can grow pulsing xenia like it's weeds and others it just dies in. There has to be a reason, but I have no idea what the answer could be.
In my previous fuge I was growing cheato and razor caulerpa and the razor would usually get choked out by the cheato. I may try that again and a couple of mangroves once this one is up and running to see how things work out. I won't use grape caulerpa again though, I had it once and it got into my main tank and was a pain to get it all out. Just a warning about it, it's great and a fast grower just make sure it stays put in your sump.