The pleco could eat it easily but obviously doesn't want to eat it. A magnetic algae float will indeed work. How long are you running your lights for daily? When having an algae problem reducing your lighting down to 6 hours daily will help a lot.
Then it must be something along the lines of green spot algae but bigger. Only nerite snails are able to scrape that off and eat it. I'd still only run lights 6 hours daily. Do you know what your nitrate reading is?
My guess is light is your main problem. Adding more plants can also help as they use the nutrients that the algae does.
What about a UV sterilizer?
Won't it kill the algae in the water column? Might not completely get rid of it but it should help. But I can't see the pics he put up so not sure what kind of algae he's got.
You need to do some research on all the various types of algae. As said a UV will only kill green algae bloom which is green water. It has nothing at all to do with algae found on the glass, plants, and decorations. Those algae's which include what the OP has is not in the water column therefore a UV will do nothing for them. I already suggested what is the best way to start addressing the algae problem the OP has, which is for starters only running the tank lights 6 hours max until the problem causing the algae is fixed. A UV would be a total waste of money in this situation.
It's the only thing right now I can suggest since I still don't think you posted your nitrate readings. Also how often do you do WC's and how much do you change when you do them. A tank gets algae because the balance between lights-ferts-CO2 is off. Is the tank planted? I need a lot more info in order to see if there is something else possible aiding in the problem.
Okay your nitrates are good. I do 50% WC's weekly but if you have a low bio-load of fish 30% would be okay. You have to make a call on that one. I would turn the heat down to around 78, not that it has anything to do with your algae but your tank doesn't need to be that warm unless your keeping fish like Rams. What I'm seeing is that your other parameters are good so your lighting is your problem. Try running it for 6 hours daily or some people find running their lights for 4 hours with a 2 hour siesta then on for another 4 hours keeps algae from having enough light time to grow. Also I would consider looking into getting a couple nerite snails as they are great to have in tanks to help keep it spotless. I keep them in all my tanks and like them because they are the only algae eater capable of scraping off hard algae such as green spot algae.