Influences of two types of substrates, natural (macrophyte, Pistia stratiotes) and artificial (plastic screen) were evaluated at 3 differrent densities (10, 20, 30%) on periphyton development, water quality and growth performance of jaraqui (Semaprochilodus insignis). Fish of average initial weight 1.46-1.69 g and length 4.15-4.26 cm stocked at 1/m2 in 46 m2 masonry tanks were grown for 120 days. The tanks were...