A Basic Approach to the Natural Planted Aquarium
A Basic Approach to the Natural Planted Aquarium
Written and originally posted by:
Byron Hosking, BMus, MA
For those considering their first planted tank, the varying methods and advice can be daunting. But setting up and maintaining a thriving planted aquarium need not be expensive nor difficult. In this series of four articles I shall describe the simple basics—water parameters, substrate, and plant requirements (Part One), nutrients (Part Two), filtration (Part Three), and lighting and maintenance (Part Four)—that I have used for more than 15 years to create and maintain aquaria like those shown in the photos of my South American and SE Asian aquascapes.
This approach is basically low-tech, although I also like to use the term “natural” because it takes advantage of nature rather than significant intervention by the aquarist beyond providing the essential elements and minimal maintenance. As plant authority Rhonda Wilson has pointed out, while we cannot make an exact representation of nature in our home aquarium, we can try to get closer, and the low-tech approach is the way. The vast majority of available aquarium plants will grow quite well under this method, though some will exhibit slower growth than they would in a high-tech tank. The lighting is not as intense and there is no CO2 (carbon dioxide) diffusion, and nutrient fertilization is minimal.
Water parameters: In their natural habitat, most aquarium plants occur in soft slightly acidic water. However, they are for the most part quite adaptable to moderately hard and slightly basic water. If fish can live healthily in your water, so should most plants, although some adapt better than others to different water parameters. Adjusting water chemistry (hardness and pH) is outside the scope of this article. Heat should be provided according to the needs of the fish, and here again most aquarium plants will adapt. Lastly on salinity; salt should not be added to a freshwater aquarium unless it is needed for purposes of specific medication. Relatively low levels of salt are detrimental to many plants.
Substrate: Options for the substrate include aquarium or landscape decorative gravel, sand, soil covered by a layer of fine gravel, or one of the specific plant substrates. Plants will grow in any of these, but some are less risky than others; I currently have tanks using all of those mentioned except for soil, and as soil can cause significant issues I do not recommend it if this is your first planted tank.
Regular (inert) aquarium gravel is preferred by the majority of planted tank authors. Particle size is important. If too large, water will pass through too easily, removing nutrients from the plant roots, and debris may collect and decompose. If too fine, the substrate may compact, preventing adequate movement of oxygen and nutrients and damaging the roots of the plants; this is the danger with sand, and if sand is used the depth of the substrate should not be more than 2 or 2.5 inches. A gravel particle size of 1 to 2 millimetres is best; it provides good anchorage for plant roots and it encourages good aerobic and anaerobic bacteria colonies with less chance of compacting. It should not exceed 4 or 5 inches, and this can be restricted to those rear areas where plants like the larger Echinodorus (swords) with more extensive root systems will be planted.
Choose a natural or dark colour; not only will the plants look better, so will the fish. Most of the fish in planted tanks are “forest fish” that occur in habitats having a dark substrate and dim light, and they will both feel “at home” and display their best colouration in such an environment. A white or "bright" substrate will cause many fish stress.
Enriched substrates can sometimes benefit, but are useless with respect to plants that are not substrate rooted. Floating plants, most stem plants, and plants that affix their roots to wood and rock will not benefit from nutrients in the substrate. Substrate-rooted plants such as Echinodorus (swords), Cryptocoryne (crypts), Aponogeton, Vallisneria, Sagitarria, etc., will benefit and show somewhat faster growth, but since all nutrients must be dissolved in the water before they can be assimilated by roots, this is not essential. With plain gravel or sand, substrate fertilization in the form of tablets or sticks is useful for heavy feeders like Echinodorus and Cryptocoryne, but even this is not mandatory for healthy, lush plants.
Aquatic Plant Requirements: Aquatic plants require light and nutrients; if these are adequate [= available in the amount needed by the plant] and in balance with each other, the plants will flourish. Botanists refer to “Liebig’s Law of Minimum” which states that plant growth will be limited by the factor necessary for growth that is least available. When one required factor is missing, not only will the plants cease to grow, but the chances are that algae will take advantage. In a well planted balanced aquarium, algae will often be present but will seldom if ever be a problem. Balance is the key: keep everything in balance, and the plants will use the light and nutrients before algae have the chance.
In Part Two, nutrients will be discussed in more detail.
 Rhonda Wilson, “Low-Tech Tanks” in her column “The Planted Tank,” Tropical Fish Hobbyist, December, 2005.
 Karen Randall, “Equilibrium in Planted Aquaria,” Aquarium USA 1998, pp. 26-33.
A Basic Approach to the Natural Planted Aquarium--Part Two
In Part One I mentioned water parameters, substrate and plant requirements that include nutrients, and this latter will be detailed here.
Nutrients required by aquatic plants number 17 chemical elements, including carbon [discussed in Part 3] and nitrogen. Nitrogen occurs in four forms in the aquarium: ammonia (NH3), ammonium (NH4+), nitrite (NO2-) and nitrate (NO3-). In the nitrification cycle, ammonia is regularly produced by the respiration of the fish and several biological processes involving fish waste, uneaten food, dead matter, etc. Ammonia and nitrite are both highly toxic to fish and plant life. In acidic water, ammonia automatically changes into ammonium which is basically harmless to fish. Nitrosomonas bacteria convert the ammonia/ammonium to nitrite, and nitrospira bacteria convert the nitrite to nitrate. However, in a well-planted aquarium, this nitrification bacteria cycle is secondary to the prime nitrifying force, the plants, and may actually be detrimental to good plant growth.
Unlike land plants, aquatic plants exhibit a considerable preference for using ammonium and not nitrate as their main source of nitrogen. Some plants can use nitrite, although it is not certain to what extent they do. Most can also use nitrate, although studies show that a majority of aquatic plants prefer ammonium and will only utilize nitrate if the ammonium is exhausted. Plants use ammonium to synthesize their proteins. When nitrifying bacteria convert ammonium to nitrates, plants are forced to expend considerable energy to convert nitrates back to ammonium. For this reason, additional biological filtration should not be encouraged in a well-planted aquarium.
In acidic water, the ammonium (converted from ammonia) is rapidly taken up by plants. In basic (alkaline) water, plants rapidly detoxify ammonia with a couple of methods into ammonium which they then readily assimilate. This rapid use of ammonia/ammonium explains why nitrification (biological filtration) is less of an issue in well-planted aquaria; the plants out-compete the bacteria. Which also explains why a new tank that is well planted will not experience “new tank syndrome” when fish are added the first day. The tank is basically “cycled” from the moment the fish are introduced provided there are sufficient plants.
Plants require a minimum level of each nutrient in order to grow normally. In some cases, an excess of one nutrient may diminish the plant’s uptake of another nutrient. Some nutrients will be present in fish food, some minerals perhaps in the tap water. But not all nutrients will be available solely from these sources. It is therefore advisable to use a comprehensive liquid and/or substrate fertilizer, depending upon the plants. Dosing with individual nutrients is generally not advisable because of the possibility of causing a nutrient deficiency within the plant, and given the narrow range in balance between light and carbon. A comprehensive fertilizer will satisfy the plant’s requirements for all nutrients in the necessary proportions.
Rooted plants, being those with extensive substrate root systems, assimilate nutrients primarily through the roots. Some, such as Echinodorus (Amazon sword plants) and Cryptocoryne, are heavy feeders. An enriched plant substrate or fertilizer tablets or sticks inserted into the gravel or sand substrate next to these plants will provide the best source of nutrients. Plants with roots attached to wood and rock, stem plants and floating plants all uptake nutrients from the water column, through their root systems and (to varying degrees) their leaves. A comprehensive liquid fertilizer may be used once a week on the day following the partial water change*, and a second dose 3 days later depending upon the response of the plants. The type and number of plants in relation to the light intensity and duration plus the number of fish and organics in the aquarium will determine how often fertilization is necessary to maintain the balance.
Part Three will look at filtration.
* This is suggested because most water conditioners detoxify heavy metals, and these include iron, copper, manganese, zinc and nickel which are also essential plant nutrients. Water conditioners remain effective for about 24 hours, so adding the plant fertilizer a day later avoids the possibility of the water conditioner negating these nutrients.
 Diana Walstad, Ecology of the Planted Aquarium, second edition 2003, p. 103, provides a chart of the nutrients and their function in plant growth. Peter Hiscock, Encyclopedia of Aquarium Plants, 2003, pp. 72-77, also explains the role of each nutrient. Also see A. Glass, Plant Nutrition: An Introduction to Current Concepts, 1989. And W.G.Hopkins, Introduction to Plant Physiology, 1995.
 Walstad, idem, pp. 107-108. Hiscock, idem, p. 73. Guido Huckstedt, Water Chemistry for Advanced Aquarists, TFH Books, 1973, p. 94.
 Walstad, idem, pp. 22-23.
 Walstad, idem, p. 111.
 Walstad, idem, p. 21
 For example, excesses of copper, manganese and zinc may induce iron deficiency [Walstad, idem, p. 13.]
A Basic Approach to the Natural Planted Aquarium - Part Three
In Parts One and Two I discussed plant requirements respecting water parameters, substrate and nutrients. In this third instalment, filtration will be described.
Filtration: Aquarium filters usually employ three types of filtration: mechanical, chemical and biological. A well-planted aquarium with a balanced fish stocking actually requires no additional filtration beyond the plants themselves; however, most of us like to have more fish, and mechanical filtration is practical for maintaining water clarity. This is not the same as “cleaning” the water, the task best performed by the plants in what Dr. Ted Coletti terms “Vegetative Filtration.” The filter will keep the water “clear” of minute suspended particulate matter by passing the water through media like disks and pads or filter floss. There is no useful purpose served by chemical filtration, and there is evidence that carbon and some other types of media remove plant nutrients, so a planted aquarium should not employ chemical filtration. Biological filtration occurs on all hard surfaces within the aquarium, considerably more than in the filter. As was mentioned in the discussion under “Nutrients” in Part Two, biological filtration in a planted aquarium may likely be detrimental to plant growth.
Mechanical filtration is therefore sufficient. In smaller tanks, less than 50 gallons, I would use a sponge filter. In larger tanks, a canister works best; it provides good mechanical filtration, and the flow can be directed and often regulated. The rate of water flow determined by the filter provides the water current within the aquarium, and this should be suited to the requirements of the type of fish in the aquarium. Those from running streams should have a suitable current from end to end to replicate their habitat. But most of the “forest fish” that we house in planted aquaria occur in quiet streams, ponds, swamps and flooded forest where the flow is minimal or almost non-existent, and such fish will feel less stressed in a calmer environment and thus be healthier. And there is also an impact on the plants from water flow that must not be overlooked.
The filter should produce a water flow sufficient to ensure the water circulates through the tank and filter. This is important for bringing nutrients to the leaves and roots, and keeping the leaves free of sediments. The rate of water flow through the filter also has an impact on the amount of oxygen drawn into the water, and the carbon dioxide (CO2) expelled from the water in what is called the gaseous exchange. Surface disturbance speeds this up, as do higher flow filtration, air stones, bubble effects and power heads—devices that should not be incorporated into a well-planted aquarium. Plants produce considerable oxygen as they photosynthesize, more than sufficient for the needs of the fish and bacteria. Extraneous water movement is detrimental in two ways: CO2 which is extremely important for plant growth is driven out of the water faster, and oxygen is brought into the water at levels beyond what is good for the plants, which have more difficulty assimilating nutrients when the oxygen level increases. This is because oxygen easily binds with many nutrients, such as iron, making them too large for assimilation by the plants. But the more significant aspect is the loss of CO2.
As plants grow they assimilate CO2 and produce oxygen; in a biologically balanced aquarium, the amount of oxygen produced during photosynthesis is considerably more than that used by the plants and fish even during the night when the process is reversed, so there should be no concern over oxygen depletion requiring more filtration. Submerged plants have difficulty obtaining enough CO2 in nature and in the aquarium; this fact is believed by many to be the reason for the inherently slow growth and low productivity of aquatic plants over terrestrial. Further, freshwater emerged plants have been shown to be four times more productive that submerged plants. The reason is because CO2 diffuses so slowly in water as opposed to air, and this limits the underwater plant's uptake of CO2 because the CO2 molecules don't contact the leaves quick enough to meet the plant's needs. Aquatic plants have to use enzymes to rapidly capture the CO2. When the CO2 levels in the water become depleted, these enzymes sit idle, so to speak, but the plant still has to provide energy to them. This results in a reduction in photosynthetic efficiency and therefore growth of the plant because energy is being wasted. Thus, anything that removes CO2 in however small an amount will be detrimental to the plant's growth.
In a natural or low-tech system, the balance between the 17 nutrients (one of which is carbon) and light has to be there; so anything that may impact however slightly can become a critical factor in less success. The one thing we cannot "control" in this type of setup is the CO2, by which I mean that it is entirely dependent upon the fish and biological processes; with light we can control it, in intensity and duration, to balance, as we can with the other macro- and micro-nutrients through fertilization. Plants will photosynthesize up to the factor in least supply. Many have planted tanks that fail because the CO2 is the limiting factor, and algae will take over because it is better able to use carbonates for carbon than most (but not all) plants. The point here is that nothing should be allowed to negatively impact the CO2 in the natural planted aquarium. For this reason, filter flow should be minimal and surface disturbance as little as possible. The plants will then be able to fully assimilate the nutrients.
The final Part Four will discuss the single most important aspect of a planted aquarium, light, and on-going maintenance.
 Ted Coletti, “Back to Basics, Part II: A Multi-Modality Approach to Livebearer Aquarium Filtration,” “Livebearers Unlimited” column, Tropical Fish Hobbyist, July 2009, pp. 34-36.
 Peter Hiscock, Encyclopaedia of Aquarium Plants, 2003, p. 29.
Diana Walstad, Ecology of the Planted Aquarium, second edition 2003, pp. 93-95, 104.
 Walstad, idem, p. 163.
A Basic Approach to the Natural Planted Aquarium - Part Four
Having discussed nutrients, substrate and water parameters in Parts One and Two, and filtration in Part Three, we come now to the light and on-going maintenance.
Light is the single most important aspect of a planted tank. In large (3 feet in length and larger) tanks, fluorescent lighting is the most efficient for the type of planted aquarium under discussion; it is low in heat production, relatively inexpensive to operate, and there are a number of different types. For smaller tanks, incandescent fixtures work fine with the compact fluorescent bulbs now available; here again, the light is good (depending upon the bulb type), heat production is very minimal, and the bulbs have more intensity for less watts so they are energy efficient.
The colour temperature of light (which has nothing to do with intensity) is expressed in Kelvin. The sun at mid-day has a rating of approximately 5778K. Full spectrum around 6500K closely replicates the mid-day sun in colour. The lower the kelvin number, the warmer (appears more reddish) the light, and the higher the kelvin number, the cooler (appears more bluish) the light. Kelvin is not always an accurate guide, as different spectrum tubes can produce different light colour.
Plants grow by photosynthesizing, and to do this they require light in the blue and red colours of the spectrum; not surprisingly, blue light also penetrates water better than other colours, but red light is also necessary. Many of the so-called “plant” tubes provide light mainly in the blue and red range, but these create a purplish hue to the aquarium, and plant and fish colours will not be natural; they are also usually far less intense so there is actually less light getting to the plants. Full spectrum light, around 6500K, includes peaks in the blue, red and green colours; the green balances, allowing the colours of the plants and fish to appear natural.
Studies have demonstrated that aquarium plants grew strongest under a combination of full spectrum and cool blue. With two tubes in the fixture over the tank, it is possible to use one full spectrum and one cool blue. Tubes and bulbs with a rating between 6000K and 7000K usually work the best. However, different manufacturers can alter the colour of the light through the phosphors coating the inside of the tube, so the light may be slightly more "cool" or blue even though the kelvin rating has not changed. In some cases, the "daylight" tubes and compact fluorescent bulbs are closest to this ideal light.
Light has to be adequate in terms of its intensity and duration. Submerged plants in nature are basically shade plants, frequently growing not in direct sunlight but in diffused light caused by overhanging vegetation. Most of the fish kept in planted aquaria are forest fish that come from dimly-lit waters and appreciate less intense light. The intensity of light should thus be minimal, just enough to provide adequate light for the plants. Another advantage is that less light means less CO2 and nutrients are required by the plants to balance.
The vast majority of aquarium plants will grow very well under less light, around one watt per gallon. This formula works with regular fluorescent lighting, the T8 and T12 tubes. T5 HO tubes produce considerably more intense light, about one and a half times more light than the same length and colour type T8 tube regardless of wattage, so this must be recognized when choosing T5 HO fixtures. Over a 4-foot 55 gallon aquarium as an example, one could choose a regular fixture with two T8 tubes, or a T5 fixture with one T5 HO tube. The advantage with two T8 tubes is being able to mix full spectrum and cool white.
In their natural habitats aquatic plants receive 10 hours of daylight and 10 hours of total darkness, with dusk and dawn being the remaining 4 hours. Using a timer is the best way to provide consistent light each day; the duration depends upon factors such as the type of plants and the nutrient availability; with insufficient nutrients, plants cannot photosynthesize and the light will promote algae [remember that law of minimum mentioned in Part 1?] Depending upon the plants and nutrients, light duration can be anything from a minimum of 6 hours daily up to 12 hours and even more. Referring back to the issue of balance: the light duration must balance the nutrients available, including CO2. During the first few weeks after setting up a new planted aquarium, monitor plant growth carefully, and be prepared to increase or reduce the duration of light accordingly. Ensure that the room allows for a minimum of 10 hours of complete darkness each day.
Putting It Together—the Balanced Planted Aquarium
As Karen Randall has noted, there are two overlapping balancing acts that must go on at the same time in order to achieve a healthy aquarium. The first consists of light, CO2 and other nutrients. The second, which is closely related to the first, is the stocking level and tank maintenance.
Maintenance in the form of a partial water change depends upon the fish load in the aquarium in relation to the water volume and plants. In a truly balanced system, the fish stocking would be in balance with the volume of water and number of plants with little need for intervention by the aquarist aside from feeding the fish and the occasional partial water change. But most of us have more fish than can possibly balance the plants and water volume, so the weekly partial water change is an essential part of regular maintenance. The reason is simple: pollution from fish waste. The solid will be broken down by bacteria into liquid, but this "crud" remains in the tank until you remove it. You can rinse the filter often to remove the solid trapped there before it breaks down, and likewise vacuum the open substrate minimally for the same reason. But the "crud" still remains. Unless you have a filter hooked up to fresh water and a drain, all filters simply circulate the water over and over, and this pollution remains. Plants can remove it, but slowly and not enough to sustain the average aquarium. The only way to remove it is the regular partial water change.
Fish produce not only waste, but pheremones into the water; these latter cannot be handled except by removal. All of this builds up, day by day. Scientific studies have concluded that performing larger water changes weekly significantly improves water quality. Water stability is usually cited as the reason for regular but smaller water changes. This may be true for water parameters like pH and nitrates in non-planted aquaria, but there is no logic in maintaining more stable pollution in a tank. No one can logically dispute that reducing pollution is a benefit and the more the better; in nature our fish live in water that is constantly changing, and only through partial water changes can we begin to approach that preferred--but in the aquarium unattainable--state. At the same time, a significant weekly water change will actually work to maintain more stability long term in the water parameters.
 K. Richards, “The Effects of Different Spectrum Fluorescent Bulbs on the Photosynthesis of Aquatic Plants,” Freshwater and Marine Aquarium, July 1987, pp. 16-20. Also Diana Walstad, Ecology of the Planted Aquarium, second edition 2003, pp. 180-181.
 Karen Randall, “Equilibrium in Planted Aquaria,” Aquarium USA 1998, p. 28.
 David E. Boruchowitz, “Time for a Change: A Mathematical Investigation of Water Changes,” Tropical Fish Hobbyist, November and December, 2009.
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