+1 you'd be safer to farm your own algae. Just pick a southerly facing window. I have a 20gal long myself used in this manner. Dose some liquid ferts and with a little help from the sun you'll have a nice carpet of algae in no time.
I have 2 leopard sailfin plecos "gibbys" that winter indoors and with my algae farm, kale, romaine lettuce, shrimp pellets and algae waffers they're getting huge. They grew 2 1/2" in less than a year.