First of all, for the purpose of consistancy, are we talking about microbubbles or mini-bubbles? Mini-bubbles would be the ones that are small but still visible. Microbubbles would be ones that are too small to see. Agreed that mini-bubbles are unsightly, but irritating to fish? You realize that mini-bubbles are quite common in the ocean (perhaps not for deeper dwelling fish though). As far as microbubbles go, even if they are doing damage (which I highly doubt they do), I don't think you're going to be able to avoid them.