You can get one whenever the tank is cycled, don't wait on Algae thinking they live off it. They don't at all. Some species *may* eat some of it but not all species. You'll need to research the specific Pleco you get, there are hundreds of species. This way you can match the diet to it's specific needs.
At the very minimum you'll want to at least give it some sort of sinking Wafer at night time when the lights are out as a diet staple. There are many Algae based ones meant for Plecos.
They also enjoy many things you have in your Fridge such as Cucumber and Zucchini.
http://www.monsterfishkeepers.com/forums/showthread.php?t=42856
Read This ^ for more detailed dietary information.
At the very minimum you'll want to at least give it some sort of sinking Wafer at night time when the lights are out as a diet staple. There are many Algae based ones meant for Plecos.
They also enjoy many things you have in your Fridge such as Cucumber and Zucchini.
http://www.monsterfishkeepers.com/forums/showthread.php?t=42856
Read This ^ for more detailed dietary information.