Hornwort, (Ceratophyllum demersum) a close second best oxygenator of the submerged pond plants and a little about fish breeding.
Hornwort is an excellent oxygenating plants and actually has a slight advantage on anacharis when it comes to fish. The hornwort foliage is like a very soft evergreen in the water. If you have trouble with the large koi (usually well over a foot long) eating anacharis or other plants than hornwort may be your [...]
Anacharis come in small bunches about 6-8 stems rubber banded together. Many on-line companies offer these with optional weights so they sink straight to the bottom and no planting or baskets are required. The weights are a malleable (bendable) heavy metal that you simply wrap around the area where the rubber band is already located at the bottom of the stems. These plants rob the water of excess nutrients rapidly and that is a great thing, they are a super filter and suck up fish waste like it was nothing. The second benefit, a superior hiding place for adult fish and baby fish fry. Baby fry grow up around anacharis and hornwort and stay hidden from larger fish that would eat them. The larger fish hide between anacharis clusters when Hawks, Raccoons, Possums, neighborhood kids with nets, or the big daddy pond nemesis the Heron come around. Having enough submerged grasses and also surface plants (water lettuce, water hyacinths, and water lilies) keep your pond from becoming the daily buffet. Anacharis should be added 1 bunch per 10 gallons of water in ponds under 5000 gallons, or 1 bunch per 20 gallons for ponds over 5000 gallons. Thats many bunches but this product is sold in quantity and is generally a one time investment. If you have enough surface plants in your pond and submerged plants you will never add a drop of chemicals to ward off algae saving you 1000′s of dollars over the years, 100′s per season so just do it right the first time.
Overall pond plants enjoy calm water, a fountain or “spitter” that splashes water on the upper side of leaves and foliage will get them to begin rotting.
Water lilies planted close to a waterfall that is turbulant or causeing the top of the pads to stay wet will cause the plant to die back.