Look up aquarium plant dipping on the web.
Chlorine bleach or potassium permanganate dips are effective against algae, and even algae spores at high enough concentrations. Sporicidal levels of bleach (1:20) can be rather hard on delicate plants.
That said, this is really not going to prevent algae unless you keep your tank in a cleanroom and disinfect everything going into the tank.. Algae spores of various sorts are everywhere. They are in the air (not all algae travel this way but many do), and on your fish when you buy them (can't really disinfect fish).
Dipping is more a method for trying to prevent uncommon and harder to kill algae from being introduced into your tank. It has value, but isn't a cure-all.
You will get algae, even if you dip every plant.