This allows the plants to use up most of the fertilizer and start preparing for winter. Most will grow in water 3 to 5 feet deep, and some even deeper. Start by placing the lily in shallower water, and gradually move it deeper as it adjusts. Keep small bog plants shallower, while tall ones, such as mature yellow flag iris, can live in water a foot or more deep. The best way to control algae is the natural way, with plants and scavengers.
Plants are by far the most important, as they compete with the algae for light and nutrients.
We recommend covering about half the pond surface with plants, leaving plenty of surface for viewing fish. Japanese trapdoor snails will help control algae if used in addition to plants, and will also eat leftover fish food. As plants start to come up and cover the water surface the algae should die back. If you have an algae problem, don't expect immediate relief with plants and snails, as algae control is a gradual process. Algaecides can provide immediate relief, but the effect is very temporary, and most are harmful to plants and stressful to fish.