How are my plecos suppose to.....?

How are my 2 albino bristle nose plecos suppose to realize the algea waffers when my shrimp and other fish try and eat the wafffers befor the plecos even notcie them? Any tricks I could use to make sure they eat them? Cuz one of my albino bristlenose plecos is like trippled in size and the other one barely grew a few miilieters so I wan to make sure that one gets food