Abstract: A fluorescent water treatment polymer comprises at least one water soluble carboxylic acid monomer other than maleic acid, at least one sulfonated pyrene-containing fluorescent monomer, and at least one phosphino group wherein the phosphorous atom of the phosphino group is in the polymer backbone. Additional monomers can be present, with the proviso that if maleic acid is present it comprises no greater than 75 mol % of the polymer. Surprisingly, it has been found that when the phosphino group is present the polymers exhibit an unexpectedly strong fluorescent signal strength. The signal strength of the fluorescent monomer in the polymer is further enhanced when the polymer comprises no greater than 75 mol % maleic acid.