Sorry, Terry, but after I posted I went back and realized you had specified plecos in your question, but thought I'd leave it anyway. May to september sounds about right as I believe your weather is somewhat milder than ours. Here it would be june to august as we can get frost in the early part of september. A lot would depend also on pond location, sun exposure, etc. As for food, I would not worry about it for the summer... you want them to eat algae, after all, and they will help themselves to the goldfishes' food as well. Indoors, they will take almost any prepared fish foods, but try to stick with one with a high plant-based content. Also, they love lettuce, spinach, zuchini slices, and such. John