What many people do not realise is that aquatic plants need light & carbon dioxide to grow. You can use fertilisers, enriched substrate, etc, etc. If you do not provide the carbon dioxide & light your plants are unable to grow. It easier to achieve conditions conducive to growth than you may think. Firstly, your lighting should be on 10-14 hours per day, ideally controlled by a timer. You should have at least one high spec light & reflector, ideally two or more. Some fish keepers grossly overestimate the amount of oxygen fish require. It is not recommended to have any aeration in your aquarium. This is one of the best ways of stopping your plants growing. The oxygen fish require will enter through the surface of the water. Remove any air stones or turn down to the absolute minimum, ensure all water returning to the aquarium from filters does not agitate the surface. This will increase the amount of carbon dioxide in the aquarium. The addition of carbon dioxide is highly recommended for those serious about growing plants. Click here for more information on growing aquarium plants.