Adding pond plants will make your water feature more attractive and help keep the water cleaner. Here are some tips for choosing water plants for your pond or fountain. There are four categories of water plants: Oxygenating Plants, Floating Plants, Deep Water Plants and Marginal Plants. Oxygenating pond plants grow directly in the water and help introduce oxygen into the pond. A high level of oxygen is helpful for keeping algae under control. Oxygenators feed on decaying organic material like fish waste or leaves. Mare’s tail and Red Stemmed Parrot’s Tail are common oxygenators.