Plecos are/can be shy. I had one for 16 years and all it did was hide, lol But I think it MIGHT be okay in your tank for now anyway. I just bought two babies and never see them. What you can do is at night give them cucumber and leave it, I have a veggie clip. They come out at night. Your guppies are beautiful, my mom used to have a guppy tank, so did I and they would breed like crazy, they will leave the babies alone as long as they have shelter. They will breed, usually you should have 1 male to 3 females, the female will be harassed less.