Submerged pond plants are also referred to as oxygenating plants and are a must have for your water garden. Submerged pond plants compete with algae for the nutrients in the water keeping the pond clear. You don't need to fertilize submerged plants because you want them to use the nutrients in the water. They are sold in bunches of 6 - 8 stems, except Vallisneria which is a rooted plant. It is advised to use one bunch of plants per one to two square feet of surface area. The easiest way to sink them is with the lead weights, just wrap them around the base of the plant and put them in the pond. Alternatively, you can plant your submerged plants in a small pot or basket with pea gravel.