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/The Aquarium Gardener Series

Growing Aquatic Plants

by Bob Fenner

Easily done, with knowledge, patience

"My plants won't grow"; "I'm going back to plastic!" "Hey, where's my burping clam and colored gravel?" Arrgghhh, Dear Reader, how long is it going to take before the west catches on to "real aquariums", freshwater systems with live aquatic plants? I've waited through decades of excuses, house-plant larceny, blaming of undergravel filters, claims of non-green-thumbness... I can wait no longer. Here, in easy, understandable terms are the principal "reasons" and remedies why aquarists have so little success (please don't call it luck) with aquatic plants. Don't despair, help is on the way.

Verticals (Full/Cover Page Sizes Available)

Basic Aquatic Plant Living Requirements & Conditions:

Light and Lighting:

Adequate light quality, duration, and intensity is necessary for photosynthesis, "making with light", by definition. 1) What type, 2) how long and 3) how much? Read on.

1) Full spectrum, i.e. the wavelengths that our Earth receives via our star the sun are best. There are fluorescent and metal halide fixtures and lamps that will get you these. Ahem, I would point out that aquarists "kept" plant tanks long before artificial lighting; by using (in)direct sunlight.

2) Time: A good eight, ten, twelve hours per day, preferably on a timer so you don't forget.

3) Light requirements: A guestimate of how many watts or lumens per whatever can be deceiving. The depth, turbidity, dissolved color, reflectivity of the surface. species-specific needs... among many other factors all must be figured in. As a very rough rule of thumb, 2-4 watts per gallon, 30 per square foot of surface.


A consistent grade of finer (1/16 to 1/8" nominal diameter) gravel of a few inches depth is ideal. If you are sloping the substrate substantially, glass, rock, driftwood terracing should be employed to prevent the inevitable gravel-slide. "Natural" gravels are superior in many ways to epoxy-coated colored varieties; and they cost considerably less.


Is it worthwhile to place peat, and/or a loamy clay underneath your gravel? Yes, if maximizing plant health is your goal. Is it necessary? Decidedly not. Nutrients and other benefits that accrue from sub-gravel soil placement may be supplied through commercial solid or liquid supplementation, or for low-nutrient requirements, by fish food, wastes.

Filtration, Circulation & Aeration:

Some of these are desiraable to remove solids, keep the system destratified chemically and thermally, and prevent the ills of water stagnation on the bottom. All this being said, aquarists tend to over-do it filter, circulation and aeration-wise.

Adequate water movement without introducing air is the target you want to acheive. Your plants will do better with some circulation, but most types don't thrive if continuously buffeted. Bubblers of different sorts are likewise contraindicated for their role in driving out carbon dioxide. In my opinion the ideal filter/circulation unit is an inside power filter for small tanks, and an outside canister or hang on the back for larger systems. Obviously, arranging for intake near the bottom and discharging the return underwater, away from the intake is preferable.

Though their role is controversial, and can be countered with blind potting and barriers, undergravel filters are inferior forms of filtration for plant tanks.


A simple consideration you would think, but many of the plants sold as "tropical" are not. Egeria (one of the genera sold as "anacharis") foxtail (Myriophyllum), the rushes in the genus Acorus, Lagarosiphon, barely tolerate water in the mid-seventies.

Reciprocally tropical aquarium plants may die if temperatures dip much below 70 F. Like the fishes you know, plants have ranges of tolerance and optimum growing temperatures. You must investigate what these are in reference works.

Water Quality:

Can you define this elusive aqueous condition? More than just any given measure of static pH, dissolved oxygen, redox potential... water quality exists as a dynamic range and shift of many interactive values. Ideally, for us as aquarists, the concentrations and circumstances of our systems "water quality" favor (stable and optimized) the intended life in our systems.

Bringing this down to "brass tax", the things we can measure and manipulate, just what does this mean? The following:

Alkalinity/Acidity and pH

The pH of a solution is a relative measure, a point on a scale, of hydrogen ion concentration. Alkalinity and acidity are different, related and just as important; they refer to the buffering capacity of the system. In other words, the degree that chemical species in the water resist change in pH. Thus you can understand that two or more bodies of water can have the same pH, but very different buffering capacities. This point bedevils beginning aquarists; "Why won't my pH change when I add the drops/granular the way the instructions call for?", and then, "Oh my gosh, what happened, the pH wasn't shifting and all of a sudden it went off the scale?" The alkaline (on the pH scale above 7.0) or acidic (below 7.0), reserve was "exhausted" by the addition of counteracting chemical, and more added, the pH point was driven up or down.

Know this; for most localities water, alkalinity and pH are not worth fooling with. The living system which is your aquarium has a wide range of tricks to accommodate them. If you should have abnormally high alkalinity ( > 3 mEq) that your animal and plant mix disfavor, I suggest blending reverse osmosis, otherwise filtered water with some of your tap to bring the value down. Alternatively, if your water has too little alkalinity, a store bought, or home-formulated mix of buffering agents will raise the alkalinity value to a point of sustainable pH and buffering range. You want/need sufficient buffering capacity to ward off extreme shifts in pH during night and day.

A pH value that is too high can be and is a real problem in many parts of the U.S.. This phenomenon affects the solubility, and usability of nutrients and many life functions. Many aquarists complaints with live plants can be cured with an understanding and manipulation of this variable. Once again, beware; without a concurrent awareness of what buffering is and how it is related to pH, you are "playing with fire" simply trying to manipulate pH alone. A stable range of pH near 6.5 to 7.5 is desiraable, but how you get there may make all the difference. Do avail yourself of help with an alkalinity test kit, other aquarists help and enough "book learning" till you feel comfortable in altering the pH of your water.

The surest way to avoid biological troubles with these changes is to complete them in a "water change" container, like a large dedicated trash can, that you can prepare water in in advance of use, and test for before use.

Water Hardness

Is a measure of the total of mainly calcium and magnesium salts dissolved in water. Like alkalinity/acidity and pH discussed above, this is a measure that more harm is generally done through trying to change than not. Once again, should your water be abnormally hard (more than 30 dGH) or overly soft (lacking in hardness constituents) you are encouraged to blend in less solute-laden water or add the hardness in a chemical preparation.

To repeat, generally most potable water is fine to use, as is in terms of alkalinity, pH, and hardness. With age and use these characteristics become ameliorated and are most reasonably kept in agreement with regular water changing.

Carbon Dioxide

CO2 is an essential fertilizer for aquatic plants, but is it necessary to add it intentionally? Not really. Plenty of carbon dioxide is provided via respiration, decay processes, and the air-water interface. The exception to this statement is as presented elsewhere; where plant growth is "goosed" with intense lighting, and other nutrient supplementation. In these systems, not providing surplus CO2 becomes the restricting influence.

Nutrients, Major and Not:

Only a few of the dozens of types of atoms and molecules necessary to plant growth need be of concern to aquarists. Most are readily supplied by fish food and wastes. Except for newly planted and "boosted" systems with intense lighting, carbon dioxide infusion and soil augmentation, most folks can and should avoid chemical supplementation. If you're in the "booster" category, know what you're doing and stick with regular testing and maintenance, particularly frequent, partial water changes.

Phosphorus, tested free or as orthophosphate is a major nutrient, but one of minor importance to aquatic gardeners (along with sulphur, magnesium, calcium, copper, chlorine, molybdenum, zinc, manganese, boron...); these materials are added in sufficient quantity through fish feeding and water changes and are readily assimilable at appropriate pH's.

My critical exception to "don't bother with supplementation in most cases" is iron. The ferrous element is absolutely critical (it's required for making chlorophyll), and often in rate--limiting supply. Do avail yourself of a chemical source and use it in conjunction with water changes, optimally once a week.

Plants Themselves:

So, you say, "My water checks out, my tank and gravels okay, but I still can't grow those blasted aquatic plants!" Well, maybe it's the plants. Unfortunately, many plants are sold in the trade that are unsuitable; some are house plants or worse, others are so beaten by shipping and storing at the dealers that they are doomed. How to tell? Ah, there's indeed the rub.

The non-aquatics plants are easy; just study a reputable source book and you'll see no Dracenas, Spathophyllums, "pines", etc. represented as aquatic. The second issue is much tougher; for the most part you will have to rely on the honesty and expertise of your supplier(s). "But I'm not near a store that offers (real) live plants". Don't give up; chances are they can be special ordered and definitely mail-ordered from reputable outfits.

Before receiving and placing your plants, learn their requirements. Know how they're rooted and be patient; even potted plants require a month or two after arrival to adjust. Your plants may lose some, most or all their leaves before taking; don't move them.


Can be considered temporally; daily concerns are feeding your fishes, keeping an eye that all seems well. Weekly matters might be trimming back excess growth, removing snails. More than, or weekly water changes give pause for the above and the opportunity to reduce total dissolved solids and organics (heavy water), preserving alkaline buffering capacity. A monthly-plus routine includes all this, plus possible soil augmentation (through pellets, pads... to half to yearly tear down).

Remember this; stability through regular minor disruption (i.e. maintenance) is better than constant efforts at achieving a given set of desired measured water qualities.

About medications: copper and other metal-based treatments, added salts are all harmful to plants. This is once again, a/the reason for proper quarantine before introducing livestock into a main/display system; to avoid such treatments. It is also one of the main benefits for pre-treating your water-change water a week or more in advance. Such preparation does much to settle out free metal and eliminate sanitizer in your tap.

Know your livestock, is the best advice a fellow pet-fish ichthyologist can offer. How big do the plants get, how do they grow and reproduce? And, yes, there are fishes and invertebrates that will tear or eat up your plants. Avoid the thrashers, and if you must have snails, use the non-bisexual varieties (to facilitate their removal).


Growing aquatic plants is not hard; it doesn't require a science degree, big money or voodoo; just some baseline understanding, preparation and patience. I will assure you much more success with aquatic plants by doing less than more on their behalf. The most I fool with regularly is adding iron.

A simply set up and operated system with minimal lighting, water quality manipulation and supplementation will grow plants suitable for aquariums. For spectacular tanks like those in shows, magazines and books, increased applied knowledge and perseverance are all that are required.

Bibliography/Further Reading:


Baensch, Hans & Rudiger Riehl. 1993 (English). Aquarium Atlas, v.2. BAENSCH, Germany. 1212pp.

Brunner, Gerhard. 1966 (English). Aquarium Plants. T.F.H. Publications, NJ. 159pp.

Fenner, Bob & Candy. 1982. An argument for live aquarium plants and some suggestions. FAMA 3/82.

Fenner, Bob & John G. Pitcairn. 1987. Caveat emptor! Don't buy non-aquatic plants for aquaria! FAMA 11/87.

Fenner Bob and John G. Pitcairn. Success with aquatic plants; pt. 1. Rationale, buying, keeping; Pt.2, Maintenance; pt. 3. a good selection. Hobbyist version: FAMA 12/88, 1,2/89. Industry version: Retailing aquatic plants, Pet Dealer 8,10,11/89.

Fenner, Bob. 1989. Frequent partial water changes. FAMA 4/89.

Fenner, Bob. 1994. Water quality. FAMA 4/94.

Fenner, Bob. 1994. pH, Alkalinity, acidity and you! FAMA 11/94.

Gasser, Robert A. 1979. Some old (or are they new?) thoughts on aquarium keeping. FAMA 2/79.

Hovanec, Tim. 1996. Water quality; freshwater. What fishkeeping is really about. AFM 6/96.

Jeffries, Owen. 1995. Substrate and liquid additives for improved plant growth in aquariums. FAMA 6/95.

Las, David A. 1996. Look ma- no filter! FAMA 2/96.

Randall, Karen A. 1996. CO2 supplementation in the planted tank. TFH 3/96.

Riehl, Rudiger & Hans Baensch. 1987 (English ed.). Aquarium Atlas. MERGUS, Germany. 992pp.

Roe, Colin D. 1967. A Manual of Aquarium Plants. Shirley Aquatics, England. 111pp.

Stodola, Jiri. 1967. Encyclopedia of Aquarium Plants. T.F.H. Publications, NJ. 368pp.

Walstad, D.L. 1993. Plant nutrient availability in the aquarium. FAMA 5/93.

Also, please see the Aquatic Gardeners home page and jumps via your computers search engine, and "fishy" electronic bulletin boards (many have aquatic green thumb sections).

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