The toilet cleaners according to the invention are in tablet form and contain terpolymers of monoethylenically unsaturated dicarboxylic acids, monoethylenically unsaturated monocarboxylic acids and other monoethylenically unsaturated monomers. Moreover the last-mentioned monomers on hydrolysis yield monomer units which contain at least one hydroxyl group in the carbon chain. The toilet cleaners are distinguished by improved biodegradability.
