A method is described for selecting a treatment additive for aqueous systems, in which crystal habit modification properties are prioritized; for aqueously preparing a substantially poly-maleic additive through in-situ formation of maleic acid copolymer so that mono-carboxylic acids, non-ionic functional groups, and terminal hydroxyl groups are also formed during polymerization; and for applying such additives for treatment of aqueous systems. Treatment agents resulting from these processes are also described.