Any advice on keeping dragonfly larvae out of my tubs? I realize that I could put screen over the top but I would like to have mosquito larvae for the guppies to feed on but don't want dragonfly nymphs feeding on my guppies. I had almost an entire tub of Blue Moscow fry consumed by the little monsters a few years ago and I haven't put guppies outside since then. I know that dragonflies are beneficial, but I don't want to feed my guppies to them. I was wondering if a top made from hardware cloth or chicken wire would allow mosquitos in and keep the dragonflies out. I am also concerned about the effects of the metal over the water when it rains. Any suggestions?