Tagged scale-inhibiting polymers, compositions comprised thereof and preventing or controlling scale formation therewith, the tagging units being units deriving from a monomer having the formula X2C═CYY′ wherein X is a hydrogen atom, or a C1-C4 alkyl radical, Y is a hydrogen atom or a C1-C4 alkyl radical, Y′ is a radical having formula -L-Arom, wherein L is a covalent bond or a divalent organic linking group optionally comprising heteroatoms, and Arom is a group comprising at least two conjugated aromatic rings, said rings comprising conjugated carbon atoms, and, linked to said carbon atoms, hydrogen atoms or other substituents.