Duck weed is CRAZY!! Very nutrious for your fishies too! And since it grows so fast its like a sponge for nitrites and nitrates...crazy kewl stuff! I put about half a teaspoon in my 20gal...and with in 2 weeks i had a half an inch layer covering the ENTIRE surface of my tank....OY! It grows sooo fast! Barely able to keep up! Can be a pain to get rid of too! Once its in the tank....it stays!!
