Hey Benji,
I believe the tunze ecochic grows chaeto as well as the kessil. I used them both on different systems during the same time period and found the chaeto to grow well in both systems with both lights.
The tunze is submersible which can give you different options on how you light your refugium. The tunze mounts with a magnet bracket type system. Which could be limiting depending on how big your fuge is and how it’s set up. The kessil either hangs or uses the gooseneck so can require a bit more room over head.
The kessil has adjustments in color and intensity which the tunze does not but I find once I set the kessil I do not adjust it after, so those adjustments aren’t a big deal at the end of the day for chaeto.
I wouldn’t have a problem using either one to grow chaeto. They are both good lights. It depends on your budget, space and setup as which one will be the best for you. Hope this helps