Today I noticed a darker discoloring along the bottom of my pool where the botton ond side seam together on a slight angle (those familiar with vinyl liner pools know where I'm talking about). Otherwise, water is clear and clean. My first thought was algae. Being new to pool ownership I thought I would throw it out. Anyone have any thoughts on if this is likely algae or not? Can algae be present like this in an otherwise extremely clean looking pool? I brushed it off and jacked up the bleach slightly higher than normal (but not near shock level). Should this be sufficient treatment (assuming it is algae)?