Mainstays Large Plastic Bulk Food Storage Canister with Lid and Handle, Pantry Organizer Container for Cereal and Dry Food Storage, 46 Cup Capacity, Dark Gray Lid, 11.55" x 7.8" x 13.25"

Even with zero inputs algae grows. I have one of these things I got from Walmart as a water container for my chickens. I installed one of these watering cups on it, and drilled a pinhole in the top for air to get in (otherwise I get vacuum and the cup won't fill) Every once in a while I have to clean it out because algae gets in there. Not really any input nutrients other than sun and water.