A Basic Approach to the Natural Planted Aquarium
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 article I shall describe the simple basics that I have used for more than 15 years to create and maintain aquaria like those shown in the photos of my aquascapes. [Endnotes appear at the end of the second post.]
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. The 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.
Aquatic plants require light and nutrients; if these are adequate and in balance, they 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.
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.
Substrate: Options for the substrate in the method under discussion include aquarium or landscape decorative fine gravel, sand or one of the specific plant substrates; regular (inert) aquarium gravel is adequate and preferred by many. 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 causing plant root deterioration. If too fine, the substrate may compact, preventing adequate movement of oxygen and nutrients and also damaging the roots of plants. A 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. 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.
Enriched substrates can help, 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. And substrate rooted plants such as Echinodorus (swords), Cryptocoryne (crypts), Aponogeton, Vallisneria, Sagitarria, etc., will assimilate nutrients from the water column as they pass through the substrate; substrate fertilization in the form of tablets or sticks is useful for heavy feeders like Echinodorus and Cryptocoryne, but not even this is mandatory for healthy, lush plants.
Nutrients required by aquatic plants number 17 chemical elements , including carbon already discussed 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. Nitrosomonas bacteria convert the ammonia to nitrite, and nitrospira bacteria convert the nitrite to nitrate. Ammonia and nitrite are both highly toxic to fish and plant life. In acidic water, ammonia basically changes into ammonium which is basically harmless to fish.
Unlike land plants, aquatic plants exhibit a considerable preference for using ammonium and not nitrate as their main source of nitrogen . At least 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 because the assimilation process is quicker. 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. This 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. Root tablets or sticks inserted into the 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 leaves. A comprehensive liquid fertilizer may be used once a week following the partial water change, and a second dose 3-4 days later depending upon the response of the plants.
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, filter rock, 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, and in a well-planted tank the nitrification bacteria will be considerably fewer in numbers due to the biological actions of the plants is using ammonia. There is actually more biological filtration occurring throughout the aquarium than in the filter . 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 . 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.
Light is the single most important aspect of a planted tank, and 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.
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. Light below 4000K appears reddish (warm), and light above 7500K appears bluish (cool). Full spectrum around 6500K closely replicates the mid-day sun in colour.
Plants grow by photosynthesizing, and to do this they are most proficient using light in the blue and red colours of the spectrum; not surprisingly, blue light also penetrates water better than other colours. Many of the so-called “plant” tubes provide light mainly in the blue and red range, but this will create a purplish hue to the aquarium, and plant and fish colours will not be natural. 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 stronger 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 rated around 6500K and one cool blue having a slightly higher Kelvin rating.
Light has to be adequate in terms of its intensity and duration. Submerged plants in nature are basically shade plants, growing not in direct sunlight but in diffused light caused by overhanging vegetation. Bright light is consequently not required for the vast majority of aquarium plants that will grow very well with 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 70g 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 a duration of 10 to 12 hours of tank light each day. Ensure that the room allows for a minimum of 10 hours of complete darkness each day. 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.
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. The methods outlined in this article will allow the aquarist to establish just such a balanced steady state aquarium.
 Karen Randall, “Equilibrium in Planted Aquaria,” Aquarium USA 1998, pp. 26-33.
 Diana Walstad, Ecology of the Planted Aquarium, second edition 2003, p. 103, provides a chart of the nutrients and their function in plant growth.
 Walstad, idem, pp. 107-108. Hiscock, idem, p. 73.
 Walstad, idem, pp. 22-23.
 Walstad, idem, p. 21
 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, idem, pp. 93-95, 104.
 Walstad, idem, p. 163.
 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 Walstad, idem, pp. 180-181.
 Randall, idem, p. 28.
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