First, how did you get rid of the Eur Milfoil? If there are indeed bubbles coming out of dead material, that would mostly likely be CO2, and that material is taking out O2. Not a good thing. The milfoil was taking up the excessive nutrients, and when you killed it all off something new and exciting took it's place, and it ain't tree pollen. Real live red algae is normally marine algae, not freshwater. It's possible something is also killing off the algae and sending it through a dying color change, from green to red to brown. Nice photos. Would help if I knew what you used to kill the milfoil, and it would help you to get that dead material out.
