Algae Walfer?

I have 2 otocinclus,3 neon tetra, 1 red nose tetra, and 2 guppys in my 5 gallon tank ( I know it is over stocked). Anyways my otocinclus fish hate ate all the algae from my rocks and tank. They are runnning out of food to eat. When I drop a algae walfer in the tank the guppys and other fish eat it all. Do you know how to stop this?