Hi Robert. Welcome to the forum.
This topic has been discussed quite a bit. The easiest way for you to see what's been said and if it is of any help is to do a search:
After you log in, you will see several words in a gray bar across the top of the page. Click on the word "Search" and enter in the word "algae" in the drop-down box. You will see a dozen or so threads you can peruse to see if they are of assistance.
With my s/h pots that face the sun directly, i cover up the side exposed to direct sunlight with opaque paper. the algea eventually dies off and leaves nasty brown residue on the pots. aesthetically unpleasing but it keeps the algea away and i dont have to keep watering with a physan solution every so often.
I have alot of algae growth, but I try to ignore it. I have heard that to prevent it from growing you can add a couple of drops of Physan 20 to the water, every time you water, from as soon as you pot the plant to the time it dies. That's too much work for me. You can also use dark pots to cover the outside of the clear ones to prevent light from reaching the algae.
Like I said, I just ignore it. If centipedes and roly-poly's don't harm roots, algae shouldn't either.
I have heard of people putting aluminum foil around the s/h pots or spray painting them black. I personally don't do either of these because I like to see the water level easily. So I live with it. They say the algae does not smell but I think it does.