CO2 eats algae

This sounds like a bad science fiction horror movie.

I have a waterlily growing in a clear plastic container outside. Roughly 6 gallons. I have a water pump 130 gph aerating water. Algae grew so thick I could no longer see the pump or submerged plant. Very cloudy and dense. Two days ago I put 2 cups of seltzer water in it to see what would happen. The water started to clear a bit. The next day I put a liter of seltzer water and I could see the pump and plant again. Fascinating.

would that harm the roots?

No, check out the pics on my other thread. ph and co2. The pictures are of the roots using only lucas formula and co2. The roots are white healthy.