BN plecos can be fickle it seems. I've had groups that cleaned algae and slime really well (I used to use them in discus tanks for the slime build-up) and others that won't touch it. I currently have five BN plecos in various cichlid tanks here and all they eat is pellets, bloodworms, algae wafers, and veggies. They refuse to even get on the glass.
I just ordered some Nerite snails so I will keep you posted on whether or not that works better.
I just ordered some Nerite snails so I will keep you posted on whether or not that works better.