Your stock hood and light would be a good place to start. If you have glass in your hood, it is filtering out the U.V. before it even hits the water. Also, fluorescents lose their ability to create U.V. as they age. If your lamp is on more than six hours per day then you should be changing the bulb every six to eight months. Both of these factors could also lead to increased algae growth as lower plant forms will thrive when the environment will not promote other plants like your sword from doing as well.