I have two waterers. One is a 5 gallon buket and the other is a metal one from the store. I am noticing when I clean them out to put freash water in them they have green alge in them. Mostly around the lid of the 5 gallon bucket. It is white so I can see it better but it is in both. Is there anything I can add to the water that will keep that from happening? That will keep the water clean. I worry when I am gone for a week and they don't get cleaned as often.