Starting with the pioneering work of Ein and Lazarsfeld [EinLaz93] restrictions on values of Seshadri constants on algebraic surfaces have been studied by many authors [Bau99, BauSze11, HarRoe08, KSS09, Nak05, Ste98, Sze12, Xu95].In the present note we show how approximation involving continued fractions combined with recent results of Küronya and Lozovanu on Okounkov bodies of line bundles on surfaces [KurLoz14, KurLoz15] lead to effective statements considerably restricting possible values of Seshadri constants. These results in turn provide strong additional evidence to a conjecture governing the Seshadri constants on algebraic surfaces with Picard number 1.