Here's what he said ". . . for reasons unclear, the algae has never outgrown the filter and has never had to be removed or harvested, . . ." Here's the link to Palletta's review of Leng Sy's Ecosystem in 1997 Volume 14 Seascope if you want to read his whole article. The .pdf has all four issues so you'll need to scroll through them to get to the summer issue it's in.
Here's the best example I have: Initially Calurpa growth was pretty robust and was a fair amount was harvested from the two ~40 gallon refugiums 3 or 4 times the first two years. It was harvested only one more time after that and the last two years even though there was a fair amount that showed some growth with new runners overall there wasn't any significant changes in volume and none was harvested.
And here's a video of the system.