Scale-inhibiting polymers comprising one or more scale-inhibiting units and one or more tagging units, wherein each tagging unit is formed from a compound of Formula I, II, III, or IV, or a salt, hydrate, salt hydrate, stereoisomer, dehydrate or derivative thereof. Scale-inhibiting compositions comprising the scale-inhibiting polymers, processes for determining a concentration of a scale-inhibiting polymer for inhibiting scale formation, and methods for preventing or controlling scale formation in systems comprising fluid circulation with the scale-inhibiting polymers are also disclosed herein.