Ask the WWM Crew
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Successful pond water quality management can be approached from two different mentalities: "motor cruiser" or "sailboat" to label these philosophies for nautical types. The former embodies "mastering" the system with large pumps, mechanical filters, perhaps ultraviolet sterilizer technology, chemical filtration, testing and addition of products to "keep the water right". On the other end of the spectrum, the sailboat approach to pond-keeping involves passive countervailing strategies to maintenance. Perhaps shading the pond surface to an extent, a much larger non-pressurized biological filter area/volume, and the use of what is called "oxygenating grasses".
Oxygenating grasses are a group of plant species defined by their function and utility more so than their taxonomic affinities. None are actual true grasses (family Graminae), but either as unattached or rooted, totally submersed or emergent forms, appear "grass-like" in morphology. These "grasses" provide useful functions for pondkeepers in the ways of oxygenation, use of carbon dioxide, uptake (bioaccumulation, nutrient transport) of nutrients like nitrates, phosphates that might otherwise fuel pest-algae overpopulation growth, make habitat for juvenile fishes and other beneficial life, and are decorative; beautiful in their own right.
On the few downsides of their use, such plant life can become a nuisance by simple overgrowth, clogging pump impellers, plumbing intakes. If allowed to overrun a system, oxygenating grasses can actually cause too-wide swings in daily water chemistry and physics, or crowd out other purposeful livestock. These potential problems are easily prevented by regular maintenance; the removal of extra plant material.
However, there are as usual some simple provisos to follow in choosing, selecting and placing these forms of life. Some species are more tropical/cold water, they all have different ranges/tolerances of aspects of water qualities such as pH, hardness, water movement, light intensity. Herein are ideas on the use of the most common varieties available and their appropriate use.
Oxygenating Plants Called Grasses: The Players
A list of what might be included here might be long indeed. There are hundreds of suitable plant species for the stated varied jobs above. Human nature being what it is, there are favorite genera of plants used trans-globally. The following are most often available worldwide.
What's in a name? Plenty when it comes to this group of species of oxygenating grasses. Most "Anacharis" sold in the ornamental aquatics interest is Egeria densa Planchon, a tropical species not suitable for cool to seasonally cold pond use. Of the species of plants you may find labeled as such this is the largest, most "dense" Elodea, with leaves to over an inch in length, with rounded tips, in whorls of three or four.
The cooler water species like Elodea canadensis Michaux 1803, have smaller leaves (about 1/3" by 1/8" that appear bent inward on their axis. These coldwater species are notorious for "falling apart" in aquariums and fish bowls (where Egeria should be used), but very appropriate for outdoor pond use.
Ceratophyllum: Hornwort, Coontail:
A single genus of rootless plants makes up the family Ceratophyllaceae. Found worldwide. A good group of plants that have species for both tropical aquariums to cool-water ponds. Prized for fast growth, nutrient absorbing properties (this along with its chemical production aids in reducing algal growth), tolerance to varying environmental conditions (used for removing hardness by some Waterlily culturists) and its lack of palatability to fishes.
Myriophyllum: Parrotfeather, Water Milfoils
The milfoils or parrot feathers, what a beautiful name, of the genus Myriophyllum ("Mere-ee-oh-fill-um") encompass species of hardy and adaptable plants for all aquaristic endeavors; cool, cold, tropical aquariums, even ponds. Most of the ones sold are grown outdoors in temperate ponds, rooted, and have flowers borne on aerial shoots?
There are some hundred species worldwide, most coming from temperate zones. Some varieties are aquarium-useful, and many others are amphibious bog plants that only live partly submersed for the wet season. Still others are free-floating to rooted plants suitable for ponds.
Milfoils or parrot feathers are characterized by their soft stems bearing whorls of fine feather-like leaves. Their flowers are borne on aerial shoots. If space between the aquarium top and the water's surface can be made, some portion of these plants should be encouraged to grow aerially. This for sheer beauty as well as enhanced plant metabolism.
Sagittaria, the Arrowheads:
"Sag's" are easily grown in aquarium to bog circumstances. Indeed, Sagittaria tubers have been human food staples in Asia and North America before recorded history. There may be sixty plus species in this genus, some small, others tall, with very different submerged and emergent growth that in turn is variable depending on light and other growing conditions. Aquarium hobbyists may at first be surprised to find that there are larger, growing-out-of-water types of "Sag", but have likely seen these in viewing aquatic gardens.
Called Arrowheads for their distinctive pointed emersed leaves, these plants are best rooted in sand covered soil where they will quickly reproduce (in warm seasons) by asexual runners though this family of plants (the Water Plantains, Alismataceae) does indeed reproduce sexually through flowering. Most folks use plastic trays to contain these adventitious plants, but any soil-holding container will do.
Taller, narrower-leaved and generally not as deep green in color as the similar appearing Arrowheads, the genus Vallisneria are land-grass like plants that live entirely aquatic lives. The most appropriate, about only sub-tropical species offered in the trade is "American" or Jungle Val., Vallisneria gigantea. Native to New Guinea and the Philippines, this up-to six foot long beauty is now widespread worldwide; for example, growing year round in ponds in Southern California.
Like Sag.s, Val.s are grown in closed containers of soil or gravel with care taken to not crush their sensitive thick, white roots on planting. They similarly reproduce by asexual runners and occasional flowering.
What? Is this all!?
Where are Ludwigia, Cabomba, the many Duckweeds, et al.? As previously stated, this is but an introductory piece on the topic. There are MANY more species that can/could be used as "oxygenating grasses" as you will find.
Do be aware that the above genera do contain species, sports of differing environmental tolerances. Seek to know which you are dealing with, or seeking, to match your growing and weather circumstances. Though they may superficially appear the same, some species of the same genus are much more cold or warm water. The best way to be assured of having pond-useful materials is to work with a knowledgeable supplier of same.
Over-wintering, perhaps Over-Springing, Falling:
Though often not appreciated till too late, many of the varieties, species of plants offered for pond use don't tolerate the highs, lows, or vacillating temperatures of many systems. Do utilize a thermometer and log your recordings of activity and measure in your pond/s... and be ready seasonally to do what must be done to assure your livestock's survival. Happily, most of the oxygenating grasses are very quick growers, and if you can "bring some inside" as in a window-near aquarium or lighted "kiddie-pool" in the garage, yours should bounce back once warm weather (and water temperatures) resume.
Koi, goldfish, other minnow-fishes and snails used on purpose or "inherited" may well take a liking to grazing on many of these oxygenating grasses. Countervailing strategies to prevent outright entire consumption include clever screenings of the plant containers, floating baskets (as with a ring of drip-irrigation piping joined together with black polyethylene netting hung below), to separate growing basins or bog areas where the system water pours through.
A Note re the Biggest Pest: You and I
Please do take care not to allow these or any other non-native organism to "get loose" from your care. Even just a small bit of most "Oxygenating Grasses" getting into wild habitats where it can survive spells disaster... other, indigenous species being crowded out, over-shaded, starved for nutrients, perhaps even drowned (as in waterfowl) by too-vigorous exotic stands. Either dig a hole and bury non-native trimmings, make sure they're making their way into permanent soil-based landfills, or bag and freeze the material before sending it off in the trash.
Both approaches to pond water quality maintenance, "motor-cruiser" and "sailboat" will work in otherwise well-designed, constructed and maintained biological water features. The first requires more upfront and ongoing costs and more constant vigilance to keep a system clean and clear, the other less cost, but more concessions to the vicissitudes of nature. Oxygenating grasses should be an important component of the latter strategy type. They are the simplest way to assure good water quality, reduce pest algae control... and they're beautiful in their own right. Which one/s will you choose?
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