How do I design my refugium chamber to make the Chaeto tumble?

[AlgaeBarn]

I just want to add for those wanting to tumble that’s great, but not needed at all. I have a 150g Rubbermaid sump and keep chaeto in a laundry basket. I just restarted chaeto for fun. I started with a clump about 1/3 the palm of my hand. This is 1 week later.

So that was 1 week growth, no tumble. Here is this weeks growth, actually 1 day short, so 13 days growth from the tiny 1/3rd palm size in top left image.

So while it can be fun to experiment and tumble, it grows crazy without!

That is some awesome healthy looking Chaeto right there!!