In one example, an anti-fouling latex ink includes a liquid vehicle, a pigment dispersed in the liquid vehicle, latex dispersed in the liquid vehicle, and a polystyrene anti-fouling additive dispersed in the liquid vehicle as a free solution. An illustrative method of formulating a latex inkjet ink includes forming a liquid vehicle with water as primary solvent, dispersing pigments in the liquid vehicle, and adding 0.01 wt % to 1 wt % of a polystyrene antifouling additive as a free solution to the liquid vehicle.