Pelikan 4001 Bottled Ink for Fountain Pens, For Pelikan M205 Classic Duo Highlighter Pen, Fluorescent Yellow, 30ml, 1 Each (344879)

I think UV reactive inks that are FP friendly are mostly clear on paper and used for “secret message” type stuff. Meaning you’d have to write under a blacklight to see what you’re doing. There are some dip pen inks out there but they are NOT FP friendly. They are very clearly labeled as dip pen inks like Dominant Industry Philosopher’s Stone and Seraphinite. There are fluorescent inks like Octopus Highlighter ink and Pelikan’s Highlighter Ink, but they’re not GITD.