"Clarity is pleasurable", and it's about time we had some good feelings and cleared up a/the "anacharis question". How many types of this plant are there? Why does it now and then live like a champ and other times just fall apart? Are there anacharis, elodea and Egeria, or are they all the same?
Dear Reader, after using and selling what I thought was one brand "X" bunch plant "anacharis" over the decades, I'm coming clean. There is but one great all-round warm-water aquarium "anacharis" formerly of the genus "Elodea" now Egeria, a few coldwater varieties (unfortunately all-too-often mis-sold as tropicals) and the "other" names are fallacious.
Well, all this will be fully revealed below.
Classification & Species of Use To Aquarists:
What's in a name? Plenty. In the case of discussing the plants here, the common name "anacharis" used to be a valid genus name for some of these plants; and is a moniker still often used. The correct scientific name for most species of "anacharis" is Elodea ("Ell-oh-dee-ah"). Egeria is another recent (1961) erected genus for a similar plant (the one of most interest to aquarists) that produces 2 to 4 flowers (Elodea only 1), that have large and deeply white petals (versus small and colorless), and are pollinated by insects (elodeas is done via water).
Elodeaand Egeria are members of the aquarium-important frog's-bit family (Hydrocharitaceae). They're joined there by such notable plant genera as Blyxa, Hydrilla, Lagarosiphon, Limnobium, Ottelia, Vallisneria, et al..
We'll list the "king of anacharis" in the genus Egeria, the three most common species of Elodea encountered in the trade and one that is oft mis-labeled as an elodea.
Anacharis, elodea, waterweed for its unappreciated peskiness.
Synonyms:Elodea densa (PLANCHON) CASPARY, Anacharis densa
Natural Distribution & Ecology: Argentina, Paraguay, Uruguay, Brazil. Good for cool to tropical aquariums.
Physical Description:The largest, most "dense" elodea. Leaves with rounded tips, in whorls of three or four, to over an inch in length.
Elodea canadensis MICHAUX 1803
Canadian elodea, anacharis, Canadian water pest.
Synonyms:Anacharis canadensis, A. alsinastrum, Serpicula occidentalis, Elodea latifolia
Natural Distribution & Ecology: From North America, introduced elsewhere, esp. Europe; as you might guess, a cold water species (45-65 F.).
Physical Description:Smallish (1/3" by 1/8") leaves arranged on a brittle axis usually in whorls of three (occasionally 2-5). Leaves recurved in shape.
Elodea nuttallii (PLANCHON) ST. JOHN 1920
Synonyms:Elodea minor, Anacharis nuttallii, Serpicula occidentalis, Elodea occidentalis
Natural Distribution & Ecology: North America; colonized in Europe. Another good cold aquarium or pond plant.
Physical Description:Leaves regularly in whorls of 3, (sometimes 4 or 5) about 1/4 by 1/32". Leaves gently bent and curled.
Elodea callitrichoides (RICHARD) CASPARY
Synonyms:Anacharis callitrichoides, Elodea ernstae.
Natural Distribution & Ecology: Chile; introduced into the U.K.. Cool aquariums (to upper sixties maximum). This species is all too often sold as a tropical; it's not.
Physical Description:Leaves 1/4 to 1/2 inch in length.
Elodea crispawe'll mention as a common misnomer; this plant with long, recurved leaves is actually Lagarosiphon major (RIDLEY) MOSS.
Elodeas can be grown free floating or rooted.
Substrate/Soil:Sand or gravel bottom. A general mix of peat and clay in gravel is de riguer.
Light/Lighting (intensity, spectrum, duration): 10-20k lumens; these plants grow more quickly with brighter lighting.
pH, KH, Other Chemical:Wide pH tolerance (6.0-8.0), moderate to hard water (5-20 KH).
Temperature Range:Species specific; of those listed, only Elodea densa is suitable for tropical aquariums.
Species Kept With:Outdoors and in cool aquariums, Vallisneria, Ceratophyllum, Potamogeton; and in ponds with waterlilies and spatterdocks. The more warm water E. densa with plants it will not overly over-shadow.
Trimming:Planted forms should be periodically trimmed by pinching, cutting off the upper, growing portion and replanting it, discarding the lower.
Generally by side shoots or cuttings; rarely via seeds.
Take care when initially introducing Egeria, as it is generally grown under poorly controlled conditions outdoors and will harbor snails and other pests. It should be run through a preventative dip or quarantined before using.
Waterweeds to some, the "anacharis"s Elodea and Egeria have something for every type of wet-thumb. There are species suitable for ponds, aquariums, and ones that bridge wide gaps in temperature tolerance. Nonetheless, knowing which you are dealing with and keeping the cool and tropical species in suitable temperatures is important.
Even if you're a decided "plant hater"; do give an appropriate "anacharis" a try; Egeria densa for fishbowls and aquariums. Just a few fast-growing floating sprigs goes a long way to keep your water clean and well oxygenated.
Special Thanks: To friend and mentor, Walter Pagels, Librarian of The Intl. Water Garden Society, hydrophyte master extraordinaire, and general good all-round fellow for straightening me out repeatedly on plant biosystematic issues. Thanks Walt.
Baensch, Hans A. & Rudiger Riehl. 1993. Aquarium Atlas, v. 2. BAENSCH, Germany. 1212 pp.
Brunner, Gerhard. 1973. Aquarium Plants. T.F.H. Publications, NJ. 159 pp.
Maurus, Walt. 1996. The piscatorial verbiphile (on the genus Elodea). FAMA 6/96.
Roe, Colin D. 1967. A Manual of Aquarium Plants. Shirley Aquatics, England. 111 pp.
Stodola, Jiri. 1967. Encyclopedia of Water Plants. T.F.H. Publications, NJ. 368 pp.
1 & 2) The "real thing", Egeria densa for sale as a "rooted" bunch plant in a U.S. fish store mislabeled as "anacharis". And growing fresh-cut at a farm in southern Florida, U.S.A..
3) The real "Anacharis", Egeria densa definitively showing characteristics of its flowers (deep white petals, yellow centers).