Anacharis Care Guide: What This Plant Really Needs to Thrive

Anacharis is the plant most aquarists add first, lose first, and then quietly add back a second time. It is cheap, it grows visibly within a week, and it will forgive a surprising number of beginner mistakes - until it doesn’t. The difference between a tank full of lush, pearling stems and a tank of brown mush is almost always a handful of specific decisions made in the first 48 hours. This guide walks through what those decisions are, why they matter, and how to adjust if the plant is already struggling.

What Anacharis Actually Is

Botanical background and the Hydrocharitaceae family

Anacharis is the aquarium-trade name for the species Egeria densa, a fully submersed freshwater plant in the Hydrocharitaceae family. The family is a small, well-defined group of monocot aquatic plants that includes frogbit, tape grass, and Hydrilla. Members tend to share three traits that matter in a tank: they lean heavily on the water column for nutrition, they tolerate a wide range of temperatures, and they propagate from fragments as easily as they propagate sexually. Once you know that about the family, most of the species-level care recommendations fall out of it.

Egeria densa is dioecious, meaning individual plants are either male or female. Outside its native range, only staminate (male) plants are known in the United States. Every Anacharis stem sold in a fish store, every cutting shared in a hobbyist club, and every plant escaped into a North American pond is, biologically, a clone of a male. The species survives and spreads in the wild entirely by vegetative fragmentation - broken-off pieces that root and keep going.

The leaves are arranged in whorls of four to six around a slender stem, each leaf a few centimeters long with finely serrated edges visible under a loupe. Leaves are only about two cell layers thick, which is why Anacharis is the classic classroom plant for demonstrating cytoplasmic streaming under a microscope. It also means the plant is mechanically delicate. Handle it gently, and never leave it packed in tight rubber bands for long.

Native range and the global spread

The native range is southeastern South America: from the central Minas Gerais region of Brazil, south through coastal Argentina and Uruguay, with a few inland populations around Córdoba (USDA PLANTS). The genus Egeria itself contains only a couple of species, and “Anacharis” in aquarium literature is essentially always E. densa. Other places use “Elodea” or “Brazilian waterweed” or “dense waterweed” - all referring to the same plant. The botanical name Egeria densa Planch. is the unambiguous one to use.

Outside that range, Egeria densa is now widespread in temperate and subtropical fresh waters worldwide. The USGS Nonindigenous Aquatic Species database tracks established populations across most of the continental United States, and the species is also recorded in Europe, Asia, Africa, Australia, and New Zealand. Most of that spread traces back to the aquarium and water-garden trade.

Why Anacharis Belongs in a Freshwater Tank

Oxygenation, nitrate drawdown, and algae competition

The plant’s main claim to fame is that it does the work of three or four pieces of equipment at once. Through photosynthesis, healthy Anacharis releases visible streams of oxygen bubbles from the leaf whorls - the hobby calls this pearling. In a moderately lit tank, dissolved oxygen rises measurably during the photoperiod, and the gas exchange benefits fish, shrimp, and the aerobic bacteria in your filter.

Anacharis is a column feeder: it absorbs nitrate, ammonia, and phosphate directly from the water column through its leaves and stems. That is genuinely useful in a stocked tank, where those compounds accumulate. A dense stand of Anacharis pulls nutrients out of the water faster than nuisance algae can, which is why planted-tank hobbyists have used it for decades as a soft, biological algae control.

The growth speed is the trick. Under good conditions, mature stems push 2 to 4 inches per week, sometimes more. That is fast enough to outcompete green hair algae, staghorn algae, and most green-water outbreaks in a community tank, without the equipment cost of a UV sterilizer. The whorled leaves also form a dense lattice near the surface when stems are left to grow tall or float, which livebearer fry, baby shrimp, and small schooling fish use as cover. For breeding tanks, a few floating stems provide more usable surface area per dollar than almost anything else in the hobby.

Light Requirements

Anacharis is genuinely low-demand for a stem plant. Tropica’s plant profile lists it in the low-light category; Dennerle lists “high to medium.” Both are right, in the sense that the plant tolerates a huge range, but the target range is moderate light, not deep shade.

In practical terms, that means 2 to 3 watts per gallon of fluorescent (T5 or T8) lighting, or roughly 30 to 50 PAR at the substrate from a full-spectrum LED in the 5000K to 6500K color temperature range. Aim for a photoperiod of 7 to 10 hours per day. Going past 12 hours is rarely an Anacharis problem and almost always a nutrient or CO2 problem in disguise.

A key detail: Anacharis has a low light compensation point of roughly 7 to 16 µmol·m⁻²·s⁻¹ PAR, which is why it survives in shaded tanks. What it does in low light is stretch, not stay compact. Too little light shows up as long internodes (the bare spaces between leaf whorls), pale leaves, and stems that flop over because the plant is putting all its energy into reaching the surface. Too much light shows up as bleached or yellow patches on the uppermost leaves, sometimes combined with an algae bloom on the older leaves.

If the look you want is a thick, bushy background, lean toward moderate light, not low. In deep tanks (over 18 inches), the lower portions of tall stems often get less light than the tops; trim regularly so light reaches the lower leaves. Without that, the bottom of the stem thins and the plant looks top-heavy.

Water Parameters That Keep Anacharis Stable

Temperature, pH, GH, and KH ranges that work

The reason Anacharis is the default first plant is its tolerance. Across multiple sources the comfortable range is consistent: 60–77°F (15–25°C) is ideal, with a tolerated range of roughly 50–82°F (10–28°C). pH 6.5–7.5 is the comfort band and it tolerates anywhere from 5.5 to 9.0 in a pinch. General hardness (GH) of 2–25 dGH and carbonate hardness (KH) of 1–15 dKH both work; Anacharis adapts to soft rainwater and hard well water equally.

A few practical takeaways. It is a cold-water-tolerant plant: it happily grows in unheated indoor tanks and outdoor ponds down into the low 50s°F, and it can survive winter under an ice cap in some climates, though freezing is lethal. Tropical tanks above 80°F slow its growth and accelerate leaf melt. It leans slightly alkaline, with stable pH in the high 6s to mid 7s as its sweet spot.

The biggest mistake is not picking the wrong number; it is changing the number. Anacharis adapts to whatever stable set of parameters you give it, but it hates a parameter that swings.

CO2: optional but a clear growth accelerator

Anacharis does not require CO2 injection. Without added CO2, it uses dissolved CO2 and bicarbonates from the water column and grows at a brisk 1 to 3 inches per week under moderate light. With CO2 injection around 15 to 25 ppm, growth jumps to 3 to 4+ inches per week, with thicker stems and more intense emerald color.

If you do add CO2, ramp it up gradually. A sudden jump from 0 ppm to 30 ppm can shock the plant and trigger rapid nutrient depletion that shows up as yellowing. Start at 1 bubble per second in a 20-gallon tank and adjust based on plant response and pH behavior. Watch your fish too - CO2 above 30 ppm stresses livestock.

A liquid-carbon product (glutaraldehyde-based, sold as “Excel” and similar) is a useful middle ground for low-tech tanks. It will not match pressurized CO2, but it noticeably speeds growth and reduces melt on established stems.

Planting: Substrate, Floating, or Both

Both substrate planting and floating work, and the right method depends on your goal.

For substrate planting, remove any rubber bands, lead strips, or foam anchors from the bunch and separate the stems. Trim the bottom 1 to 2 inches of leaves off each stem - bare stem sections buried in substrate rot quickly, but a leafless stem is exactly what you want underground. Insert the bare stem 1 to 2 inches into fine gravel, sand, or aquasoil using planting tweezers, and space stems 2 to 3 inches apart so light reaches the lower portions. Expect fine white roots to grow from the buried nodes within a week or two. Once anchored, the plant does not depend on the substrate for nutrition; it is still a column feeder, so substrate type is mostly about anchoring, not about plant food.

Planting depth is the single most common beginner mistake. Burying the stem too deep causes the buried portion to rot and then the whole stem lifts. Burying it too shallow lets goldfish and current uproot it.

For floating, drop a few trimmed stems on the surface. They will hang there, develop trailing roots within days, and start pearling. Floating has two real advantages: the leaves sit right under the strongest part of the light, which gives faster growth, and it works in bare-bottom quarantine tanks, breeding boxes, and shrimp tubs where there is no substrate at all. The trade-off is appearance - floating Anacharis looks like a tangle rather than a background, so most display tanks plant it. Quarantine, fry-rearing, and outdoor tubs are usually better with floating stems.

In outdoor ponds, Anacharis often grows as a free-floating mat by midsummer. A single bunch released in spring will fill a 100-gallon tub by August under good light. The same vigor that makes it useful in a pond is what makes it a regulated plant in many U.S. states - more on that in the legality section below.

Propagation: The Easiest Job in the Tank

Stem cuttings that will actually root

Anacharis propagates from stem cuttings only. There are no tubers, no runners, and no plantlets. The plant is essentially a hollow column of nodes, and any node can produce roots and a new shoot.

A reliable sequence: choose a healthy, actively growing stem at least 8 inches long - pale or melting stems will not give you strong cuttings. Use sharp, clean scissors to cut a section 4 to 8 inches long, ideally just above a leaf whorl so the parent plant branches at the cut. Strip the leaves from the bottom 1 to 2 inches of the cutting; those leaves would rot underground or shade the new roots. Either insert the bare stem 1 to 2 inches into the substrate, or let the cutting float until you see 1 to 2 inches of new white roots and then anchor it. New growth appears within a week. Multiple side shoots often emerge from the cut end of the parent stem, which is why topping makes a tank bushier over time.

Cutting length matters. Anything under about 3 inches tends to struggle to establish. Aim for 4 to 8 inches and you will almost never fail.

Topping the plant for bushier growth

A stem that has reached the surface does not have to keep going up. Cut it back to your preferred height, replant the top cutting, and the parent stem will usually branch within a week. Repeat across a stand of Anacharis and the background fills in laterally as well as vertically.

The practical rule: trim when a stem hits the surface or starts to bend over. A bent stem blocks light to the plants below it, sheds lower leaves, and eventually becomes the kind of stem that looks like a telephone pole with a green tuft on top.

Common Problems and How to Read Them

Melting after planting

“Melt” in Anacharis is the most common complaint and the most over-diagnosed. The plant drops leaves, the remaining leaves turn translucent or brown, and the stem looks like it is dissolving. In nearly every case the cause is a transition shock: the plant was grown emersed (out of water) at a farm, and your tank is fully submersed with different temperature, pH, and hardness. The plant is shedding old leaves that were built for air and growing new leaves built for water.

The fix is patience, not panic. Trim away mushy, translucent sections so they do not foul the water. Match temperature within 2 to 3°F between the bag and the tank, especially when moving between an unheated and a heated setup. Float new stems in the tank for 30 minutes to a few hours before planting, slowly adding tank water to the bag so the plant acclimates to your parameters. Healthy stem sections usually send out new growth in 1 to 2 weeks.

Two important cautions. Anacharis is extremely sensitive to copper, which is an ingredient in many ich medications and some algaecides. Always check the label. And never try to “save” a melting stem by burying it deeper - the buried portion is the part that is rotting.

Algae, yellowing, and stunted growth

Algae on Anacharis is almost always a symptom, not a cause. The plant is doing its job (pulling nutrients) but the tank has a surplus of light and nutrients the plant cannot keep up with. The most common drivers are a photoperiod over 10 to 12 hours (especially with high light and no CO2), high iron dosing in a low-tech tank where plants cannot use the dosage, and direct sunlight on the tank for part of the day. To fix it, cut the photoperiod back to 7 to 9 hours, reduce or skip the iron dose for a few weeks, and shade the tank from direct sun. The Anacharis will usually outgrow the algae once conditions rebalance. Manually rubbing the leaves with your fingers during a water change removes the visible algae without harming the plant.

A few other clear patterns are worth knowing. Yellow lower leaves on otherwise green stems usually mean a normal shedding of older leaves that are now shaded by new growth; trim the lower leaves off and let the plant redirect energy to the top. Yellow upper leaves with pale, thin stems usually mean low light; move the plant closer to the light source, or increase intensity. Long internodes and a pale, stretched look are the textbook signature of low light, not a nutrient deficiency - the fix is more light, not more fertilizer. Black or mushy stem tips with stunted new growth usually mean a copper or medication issue, or a severe parameter crash; test the water and review anything that has been dosed in the last two weeks.

Compatibility with Goldfish, Koi, and Turtles

Anacharis is one of the best plants for goldfish and koi tanks, and that is the second most common reason people buy it. Yes, goldfish and koi will eat it. They will pick at the leaves, uproot stems, and graze a healthy stand down to bare stems. The reason it still works is that the plant grows faster than they can eat it. A single bunch in a 30-gallon goldfish tank will keep the fish entertained and the tank oxygenated for months.

For turtles and large amphibians, Anacharis is similarly useful. The Tortoise Table lists Elodea (Anacharis) as safe for clean, pesticide-free feed, and many turtle keepers use floating bunches as a salad bar that the turtle can graze without dismantling.

Three practical tips for plant-and-fish tanks. Plant multiple stems around the perimeter rather than one stem in the middle; fish will graze one corner completely before moving on, and a corner plant has time to regrow in the meantime. Use plant weights or small pots in ponds where koi like to root around in the substrate - a bunch in a small terracotta pot with gravel is harder to uproot than loose stems in a sand bed. Accept that stems will be shorter in a fish tank than in a fishless tank. That is fine; the plant is not failing, it is feeding the fish.

Legality and Invasive Status in the United States

This is the section most plant care guides skip, and it is the one that can save you from a fine. Egeria densa is not on the U.S. federal noxious weed list, but it is heavily regulated at the state level. The species is listed, restricted, or prohibited in many states, including Alabama, Connecticut, Massachusetts, New York, Washington, Oregon, South Carolina, Vermont, and Wisconsin (UC ANR; Oregon Sea Grant).

What this means practically: before buying online, check the seller’s shipping policy - many reputable retailers will not ship to restricted states. Before buying in a local store in a state where the species is regulated, ask if the stock is licensed for sale in your state; stores that do not know the answer are a red flag. Never release aquarium plants, fish, or water into local ponds, lakes, or streams, even if the species is not regulated where you live. The reason Egeria densa is now established on most continents is decades of “it will be fine in the local pond” thinking.

The species is also a regulated invasive in New Zealand, Japan, parts of Australia (Queensland, in particular), and several European countries. If you are moving across an international border, check the destination country’s import rules.

Conclusion

Anacharis rewards a small amount of attention. Get the light into the moderate range, keep your temperature stable, avoid sudden parameter swings, plant or float with the lower stem clear, and the plant handles almost everything else on its own. When it struggles, the cause is almost always one of three things: a transition shock from emersed to submersed growth, a copper exposure from a treatment, or a tank where light and nutrients are out of balance and the plant simply cannot keep up. Read the leaves, not the calendar, and the plant will tell you which of those it is.

For aquarists in regulated U.S. states, the legal layer is a real and underappreciated part of Anacharis care. Buy from sellers who ship to your state, keep the plant contained in the tank or pond, and never release trimmings into a local waterway. A fast-growing oxygenator that outcompetes algae and feeds goldfish is the same plant that, in a natural lake, can shade out native vegetation and clog water intakes. The plant does not change; the responsibility for where it grows is yours.

When to use this page vs other Anacharis / Elodea guides

• Anacharis / Elodea overview - Canonical hub for this species - care topics and problems branch from here.
• Anacharis / Elodea problems - Symptom-first path when you already know something is wrong.

Related Anacharis / Elodea guides

• Anacharis / Elodea watering
• Anacharis / Elodea light
• Anacharis / Elodea soil
• Anacharis / Elodea propagation
• Anacharis / Elodea fertilizer
• Anacharis / Elodea repotting
• Anacharis / Elodea pruning
• Black Spots on Anacharis / Elodea
• Brown Leaves on Anacharis / Elodea
• Brown Tips on Anacharis / Elodea
• Chemical Damage on Anacharis / Elodea
• Cold Damage on Anacharis / Elodea