how big is your tank? that's definitely black beard algae. plecos won't touch it. siamese algae eaters are the best algae eating fish, and will decimate that algae before you can say supercalifraliciousexpialidocious. however, saes, who like to be in groups of 3 or more, can grow to be 5-6" and they grow really fast. i've also heard that mollies and american flagfish will eat algae, although i don't have experience with it.
it is common in new tanks. i would check you water parameters, especially nitrate and phosphate levels--they should be in a 10:1 ratio. you should also begin fertilizing, check out the sticy in this forum. algae will thrive when your aparameters are out of whack, so best thing to do right now is work on getting your water chemistry balanced. that will definitely help with the problem.
hth