I have been told that if my leaves are yellow I need to add iron to my system. Does anyone know how to get proper iron that won't harm the fish. My fish are healthy and water is good but my leaves are yellow. My systems are after the Friendly Aquaponics people in Hawaii. I am going to tell them about your site, I took a 4 day class last year and am going back in April. I know though the more info I can get the more successful I will become. I already have people wanting to learn about it. I am glad I stumbled into you.