My personal experience is that if they affect vegetation/growth, I should have been able to tell a difference in the 2 growouts that have about 50% vegetation coverage before stocking any 2 years ago but I see no difference in clarity or vegetation amount. I think it's because we are talking about a beneficial organism that is much lower in the food chain. There is likely a change but it may be so subtle it's not a large visual change. Just my experience..
