I wrote about this in Tropical Fish Hobbyist magazine in the 1990s. I've heard about it from some guy n the net in eastern Europe. I tied it as a spot treatment and it had some promise searched for a systematic/general way to kill algae by treating the tank. After two years of experimenting I found it either killed shrimp or didn't kill algae.

Then I tried Excel. I called Seachem and talked to Greg, the CEO, a chemist. He said Flourish Excel is save at 10X overdose. I didn't try that but did try daily dosing at 2x and it was fine for 11 different species not varieties) of shrimp.

The big break came when Tom Barr explained to me that fast growing stem plants makes chemicals that kill algae. These are called "peroxidase complexes" and are the form of peroxide nature uses not the same as the stuff women bleach their hair with.

The other thing Tom stressed is algae needs very stable conditions to survive, if you try to grow it in a lab it isn't that easy.

Water changes really hurt it.

Here's what I do now that has never failed to wipe out algae so far and has never hurt any shrimp, snail fish or plant.

1) Remove all the algae you can mechanically
2) Remove all the water. It's why you have algae, it's no good so get rid of it.
3) Put in new water.
4) Double dose with Flourish Excel.
5) Raise nitrate to 30ppm with potassium nitrate

The next morning the algae should look a funny color and appear rather ill.

Do it again.

The next morning it should look all white and dead. Siphon it out and as well as the rest of the water that it just released it's chemicals into.

Change all the water again the next day.

There is no trace of the algae or anything to do with left now.

Use more fast growing stem plants and it should not come back. Using Excel from time to time - helps a lot there.