I currently have a fountain in my front yard which, up until now, I used a small amount of Swimming Pool Algae control to keep it clear. I discovered last week that every morning its overwhelmed with hummingbirds. I don't mind this, they seem like the moving water.
Because of this, I dumped out the water with Pool Cleaner in it, and just put in fresh, and I'm wondering if anybody here that might know of any algae control means that wont hurt the small birds?
They sell anti-algae liquid and pills for aquariums. It obviously doesn't hurt fish, but I would have to wonder if it would do anything to birds long term. You might want to check out the chemical make-up of the product and do a search to see if there is any research.
I can't vouch for it, but this product came up in google search.