While some plecos eat some types of algae, this does not get to the root of the problem.
There is obviously too many nutrients in your water, or too much light.
Light - try having your lights on for about 10 hours a day. If you have them on a timer, have the light turn off for an hour during the day. Algae hate this, but plants dont seem to mind.
Your tank may have too many nutrients. Nitrate - the product of the nitrification cycle (filteration) - fuels algae. Plants also use Nitrate. If you buy some fast growing plants in sufficient numbers they should out compete the algae for this Nitrate, and die back.
Lowering the temperature (within your fishes limits) will lower the metabolism of all living things in the tank - including algae.
Try weekly 20% water changes. Nitrate often builds up in mature aquariums over time. Also check your tap water isnt already high in Nitrate.
Ottos are extremly efficient algae eaters.
Finally, help along this process by removing as much as you can manually.