Blue velvet nudis primary food source is acoel flatworms. Thing is people have problems with acclimation as they are pretty finicky. They do also release a toxin that could potentially be harmful so another thing to consider.
At any rate, hope you find a solution for this type of reef aids. Have seen it on the rise noticeably in my LFS’.
I’ve never seen zoa eating flatworms, but that doesn’t mean there might not be a type out there. I’ve only seen zoa eating nudi, spiders, fish and some types of crab and snails.
Now I know for sure there’s flatworms that eat Euphyllia, some LPS, and SPS. They rang in sizes too. Some are the same size as a pea and some can get up to an inch long.