I would think that if algae is negatively impacted, there would also be other small organisms that would be impacted. What about the fish themselves? I don't know what their sensitivity to ultrasonic is, but at least with humans we may not be able to hear high-power ultrasonic, but it can cause headaches and a general feeling of poor health anyhow. The manufacturers claim otherwise, so perhaps my concerns are unfounded.
Reading up on it now, it sounds very interesting for controlling algae that is single-cell that uses air bubbles to gain access to surface light. It pops or disrupts the bubbles, causing them to remain on the bottom and die due to lack of light. So in other words, it is directed towards single-cell algae like BG algae and cyanobacteria, but probably does not impact more complex algae like chara and FA.
In all, very interesting technology to be able to target the nasty poisonous stuff in high-nutrient ponds.
