You can also use hornwort and najas grass -both floating plants (najas can also be planted). Remember plants need light. At least 2 watts per gallon on for 10-12 hours per day. Generally, the single flourescent light bulb in the standard hood is not enough. Check the wattage on the bulb. Incandescent lights - no good. A light strip with 2 is better depending on your tank size. This means on a 10 gal tank you need 20 watts of light. The standard flourescent light is only 15 watts. If you have a light strip with a glass top, get another light strip. This will help tremendously (on a 10 gal).
--Tim