Is this a Tunicate?

[GoReefin]

Came in as a hitchhiker

 

[ISpeakForTheSeas]

Yeah, that's a solitary tunicate - neat and harmless filter-feeder:

If you want to try and help the tunicates do well, offering some phytoplankton would probably be wise. Isochrysis and Rhodomonas or a blend containing at least one of these would be my first choice. For a more intensive diet that would likely show better results, see "Table 3" in the link below:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7347631/