Setting Up a Successful Low-Tech Planted Tank like a Pro, Part 1: The Basics

Author: Lea Maddocks

It can be difficult for a beginner to know how to incorporate plants into their setup with the amount of conflicting information out there, but a professional aquascaper breaks it down and makes it easy for anyone to start a planted tank.

Many new hobbyists transition from keeping freshwater fish to a planted aquarium. This is often inspired by the fantastic planted aquarium images available, as well as the aim of keeping live plants that look more impressive than plastic plants and keep the aquarium healthier. Indeed, live plants benefit the aquarium by providing more natural refuges (and even food) for fish and fry, oxygenating the water by day, absorbing excess nutrients, and/or releasing allelochemical defenses that may, to some extent, control algae.

Approaches to Plant Keeping

When most beginners attempt to keep plants, two approaches and outcomes are common. In the first approach, the budding planted aquarium keeper proceeds directly to the local fish store (LFS), purchases a few appealing varieties, and plants them in their current substrate. A few months later, the aquarist is often left with spindly, yellowing, or wilting plants commonly plagued with algae. Replacing these becomes expensive and irritating, and often the hobbyist returns to hardscape items and artificial plants.

The other is the ambitious aquarist who researches planted aquariums online or through other means and is inundated with conflicting advice and complex terminology relating to the requirements of their desired species. The second approach often yields more success, as forum members will recommend hardier plants and easier, low-tech ways to maintain them, but the influx of baffling information can make some wary or hesitant to learn more, preventing their development as an underwater gardener and aquascaper.

I'd like to share advice for beginners on how to start and achieve long-term success with an impressive basic aquascape with live plants while still keeping it simple. Do note, however, that this should not stop anyone from learning more about the planted aquarium hobby. If you want to create a planted aquarium that will truly wow an audience, there is much to learn and there are myriad opinions on how to get there.

Understanding Your Tank’s Characteristics

Before you start gardening, it is essential to understand your tank’s limits and the effect of its physical and chemical parameters, lighting, and livestock on a given plant species and aquascape.

Basic Water Chemistry: As with any healthy tank, you must start with a properly cycled and established aquarium with ammonia and nitrite reading 0 ppm and nitrates at 40 ppm or less (ideally around 20 ppm).

pH: A stable pH is also important for the health of your tank and for most tropical fish and plants. Buying fish suited to your local water conditions is advised over using pH-altering chemicals, as these can sometimes be stressful to both plants and fish. Some have limited capacity to remain stable in a given tank (particularly if buffering capacity is low). Additionally, mixing your water to exact pH at every water change can sometimes be tricky, causing your pH to fluctuate. A stable pH is more desirable than a fluctuating one, and while some fish and plants will adapt to something at the limits of their natural range, it is better to select fish and plants already suited to your current water.

Hardness: Water hardness is also very important in the planted aquarium. It is vital to the health of both fish and plants, though this parameter is often ignored by most new fishkeepers. Water hardness comes in two forms, general hardness (GH) and carbonate hardness (KH), which are measured in parts per million (ppm) or degrees (dGH or dKH).

GH is the total amount of dissolved salts in the tank (chiefly carbonate, chloride, and sulphate salts). Salts are an essential component of fresh water, as they are a source of calcium, magnesium, potassium, and other trace elements for fish and plants. They also affect the osmoregulation process in fish (i.e., maintenance of the internal to external salt/water balance), and a dissolved salt content above or below the tolerance of a specific species can cause a great deal of stress. Thus, it is important to maintain GH at an appropriate level via the addition of specially formulated aquarium salts (not sodium chloride or regular table salt) to increase hardness, or by diluting very hard water with soft water or RO (reverse osmosis) water to decrease it.

KH is a measure of dissolved carbonate and bicarbonate salts only. Understanding KH is especially important in planted tanks, as carbonates help a tank resist swings in pH and are commonly known as pH buffers. In planted tanks, plants photosynthesize during the day and consume CO₂, which can be dissolved in water as carbonic acid. The consumption of this acid can cause the pH to rise (i.e., the water will become more basic). At night, plants respire as animals do, and along with the livestock and bacteria, will also add CO₂, thus more carbonic acid, back to the system. This will lower the pH (i.e., the water will become more acidic). These swings in pH can harm fish and invertebrates, increasing their susceptibility to disease over time.

To buffer this swing, a carbonate acts by binding excess acid in the form of hydrogen ions to create bicarbonate. The reverse occurs at a more alkaline pH to produce a carbonate compound and release hydrogen ions and CO₂ back into the water, which can create carbonic acid that once again lowers the pH. The CO₂ released in this reaction can also be consumed by plants. Carbonates are also a source of carbon for plants when normal dissolved CO₂ and carbonic acid is low or absent. When KH, and therefore carbonate levels, is very low, usually below 3 dKH or about 50 ppm, and all available CO₂ in the water is used up by plant growth, carbonates will be rapidly used up and the buffering capacity will vanish. Without any buffering ability, plant cycles can now cause dangerous pH fluctuations.

What all this means is that it is essential in low-tech planted tanks to measure your GH and KH and ensure that both are kept above 3 degrees or about 50 ppm. A level of 4 to 6 dGH and dKH, or about 70 to 100 ppm, is ideal for both plants and most tropical fish (excluding brackish fish and African cichlids). To raise your KH naturally, you can add a little calcium carbonate or sodium bicarbonate to your water, making sure it is dissolved first. Calcium carbonate is preferred, as calcium is a far more useful supplement for fish. Do also note that adding bicarbonates may affect your pH by making it slightly more alkaline, so monitor this parameter in your tank and in any replacement water to ensure that your pH stays constant for the health of your fish and plants.

Substrate: Many newcomers use an inert and/or non-nutritive substrate such as gravel, pebbles, rubble, or sand in their tank. The type used will affect what you can and cannot plant—or whether you can plant in the substrate at all. A key point is grain size.

Gravel larger than 5 mm in diameter may cause problems, with poor rooting of some plants, as gaps may be too wide for roots to anchor properly and let nutrients from mulm or fertilizer tablets dissolve out and away into the main water column.

Conversely, small-grained substrate like sand is likely to compact too tightly for roots to penetrate deeply, and deep sand beds may also cause anaerobic zones where there is no oxygen and the flow of water and dissolved nutrients also cannot penetrate well. While some anaerobic zones can be beneficial for reduction of nitrate into nitrogen gas by anaerobic bacteria, these areas may halt proper root growth if you choose to plant near them. An ideal grain size for a planted aquarium is about 2 to 5 mm.

If your substrate is within a good grain size, plant any stem plants by making a small hole with your fingertip, plant, and back fill with substrate. Bury the plant about an inch below where the roots emerge, and gently pull the plant upward to the right level after back filling. This will let the roots orient themselves a little better.

For any rooted plant, let mulm accumulate around the base. This will break down and act as a natural fertilizer, though if the plant is large and a heavy root feeder, such as a sword plant, a root tab is ideal to bury next to it to get it going. From there, accumulated mulm will generally do the rest. Still, utilize fertilizer balls/tabs if plants show signs of deficiency.

If you want to go ahead and use a non-ideal substrate, check out the TFH Extras blog for some tips on what you can do to still maintain a beautiful planted tank.

Aquarium Space and Livestock: Naturally, the choice of hardscape and plants for a narrow and tall tank full of peaceful tropical tetras will vary vastly from one that is half the height, 6 feet long, and full of boisterous cichlids. Again, much comes down to research. Choose plants that grow to a good size for the tank, will not overcrowd it, and are compatible with your livestock.

Larger fish, active fish, and those that dig may restrict your choices to strong plants that cannot be uprooted, such as Anubias, Bolbitis, Java fern, well-tied mosses, or maybe potted swords. Smaller tanks will also be restricted—a little 5-gallon tank will look lush with various crypts, dwarf Sagittaria, pearl weed, and mosses, but you'll find that large swords and tall stem plants like ambulia, Vallisneria, and various hygros will soon overrun it and be bent out of shape in such shallow water.

Lighting: A lot has been written about lighting for planted tanks, a complex topic, but success can be achieved in a simple setup with a basic understanding of the important aspects.

There are two key components to aquarium lighting. The first is the output, measured in lumens. This is the amount of light energy reaching an area, and while few light bulbs note the lumens, you can assume in the case of your standard fluorescent bulb that more watts mean more lumens. Do note, though, that more efficient bulbs like compact fluorescent lights and T5s produce more lumens per watt than the older T12s and T8s, and LEDs are even more efficient.

The second is the color spectrum it emits and what intensity of photosynthetically active radiation (PAR) is contained therein. Essentially, PAR means the type of radiation or energy with the correct wavelength that plants can use. Happily, most aquarists need not be too concerned with these details, as most hardy plants requiring low to medium lighting will perform well under the light fixture setup provided with your tank when used with bulbs rated for plants. Still, it pays to know why, so let’s explore more.

Light Intensity and Output: Regarding light intensity and output, more light output is required with larger and deeper tanks, as lumens decrease with distance and some light wavelengths plants require do not penetrate water as well as others. If you have a larger aquarium, chances are your accompanying light fixture contains long bulbs and probably a couple of them. Together, this will keep the length of the tank well lit with intensity high enough for your plants.

If your tank came without lights, buy a fixture suited for your tank, and if you have an option, get the fixture with room for more bulbs (better to have more than less). A 3- to 4-foot tank or larger will require two to four bulbs overhead, though you can get by with less if you choose to use only lower light and/or floating plants, which will linger near the surface. For smaller tanks, a single fluorescent tube will likely work well for a normal 2-foot tank or less, as they are more shallow.

If you need to boost your lighting intensity, purchase bulbs with a higher wattage, but if you want or need more bulbs and your fixture will not accommodate them, another tip is to purchase a strip of high-intensity (and proper spectrum) LED lights. The benefit of LEDs is that they produce more lumens for a lower wattage and will save on power consumption.

For standard fluorescent bulbs, the common rule of thumb is to aim for 2 to 4 watts per gallon, and this is generally not a bad rule to follow if you are working with standard fluorescent bulbs and low- to medium-light plants. However, I find this often misleading, as a lower output will still serve well in smaller tanks that are considerably more shallow, and even a high output will fail your plants if the spectrum is not correct.

Spectrum: Visible light contains energy in many wavelengths, many producing different colors. These range from light in the red end of the spectrum through to violet, white light being a combination of them all.

Plants absorb light for photosynthesis primarily in the red and blue areas of the spectrum and reflect wavelengths they do not use, chiefly greens. Bulbs with a low intensity in these wavelengths will fail to grow good plants despite how bright they may seem. Luckily, most aquarium bulbs now have a chart on the side of the packaging showing the amount of light of each wavelength that the bulb produces. Those with large spikes in the area of 430 nm to 460 nm (blue spectrum) and 645 nm to 665 nm (red spectrum) will provide the right colors to grow your plants well, and another spike in the 500- to 600-nm region (yellow/green spectrum) will produce a nice daytime effect in your aquarium.

Photoperiod: The final all-important factor in lighting is the photoperiod, or the length of time per day the lights are left on. To encourage healthy plants and prevent algae growth, a total period of eight to ten hours with an uninterrupted dark period of 12 hours is recommended. It is also best to have this period kept regular, and some plants like crypts will melt with large rapid variations in photoperiod, so a timer is strongly advised to keep things constant. For those of us working during the day, it is certainly also an option to split the photoperiod into two lighting blocks (even or uneven) so you can enjoy your tanks in the morning and at night when you are home. A block should be at least three to four hours in length to allow plants to gear up for photosynthesis and have some time going flat out.

To Add or Not to Add CO₂

In a closed system such as an aquarium, plants will grow only as well as their limiting factor. Nutrients and light may be abundant, but some will still always have struggling plants. In most cases, it is because a lack of carbon dioxide (CO₂) is limiting any further growth. When plants are growing poorly and light and nutrients abound, algae can become an issue. Certainly, a CO₂ injection system will resolve this problem, and modern units are now available that are simple to install and regulate.

But for those not wishing to purchase these sometimes very expensive units or who do not have room under their tanks, there are options. The first is adding liquid carbon. Several manufacturers now produce this and I have found it excellent, though it can adversely affect some plants like Vallisneria.

The second is increasing turbulence. There are arguments for and against this, but for tanks without CO₂, turbulence should increase both oxygen (O₂) and CO₂ for your plants. Turbulence works by allowing better gas exchange between the air and the water and, as concentrations of CO₂ are generally higher in the air than in the water, creating turbulence or adding an airstone will increase the dissolved concentration of CO₂. This will also increase dissolved O₂, which livestock, bacteria, and plants also require to thrive. It will also prevent CO₂ and O₂ levels from undergoing excessive fluctuations within the tank due to daily plant cycles of photosynthesis. The only time turbulence will work against you is when you are already using CO₂ injection. In that case, increasing turbulence will only work to off-gas this additional CO₂.

The third option is to use a “siesta” or a few hours with the lights off during the middle of the day. Several aquarists have demonstrated that CO₂ in many planted tanks is just about depleted after 4 to 6 hours of photosynthesis. By turning off the lighting for a 3- to 4-hour period, plants cease strong photosynthesis, and dissolved CO₂ has a chance to accumulate to almost pre-light levels from plant, animal, and bacteria respiration, as well as (likely) via diffusion from the air. When lights switch on again after this period, dissolved CO₂ is in abundance for the next round of photosynthesis (see plantedtank.net and p. 179 of “Ecology of the Planted Aquarium” by Diana Walstad for further information). This break or “siesta” during the day has the added advantage of reducing power consumption and total photoperiod time to reduce the chance of algae outbreaks. It also means you can enjoy your tanks in the morning and well into the evening if you work standard daytime hours.

The fourth is to use plants with some aerial leaves or leaves that sit on the water surface (like lilies). For these plants, dissolved CO₂ is not an issue. They will not be CO₂ limited at all and will grow rapidly, with the only limiting factors being light and nutrients. It is for this reason that many aquatic plants that are grown commercially are grown emersed (i.e., above the water) before arriving in stores. In this vein, most aquatic plants are also capable of producing aquatic leaves and aerial leaves, so given time and opportunity, your plants will happily rise above the waterline—though check with your local store to be sure. Plus, some leaves protruding from the tank can look very effective. Just be sure to raise your lights above them by at least several inches to a foot (depending on lighting intensity) to avoid overheating/burning the tips.

Finally, avoid planting too heavily or use slower-growing plants such as Anubias and Java fern varieties if your tank is lightly stocked, and use more driftwood and rock to create a natural feel. Adding fewer plants can ensure that your tank’s CO₂ resources are not rapidly depleted, which can be dangerous if your KH is low.

Fertilizer Requirements

Fertilizer requirements depend on what you are growing, how fast plants are growing, and your stocking level. In a lightly planted tank with several fish, good feeding, and hardy, slow-growing plants, the need for additional fertilizers is probably nil. For large, root-heavy feeders (such as Amazon swords), it may help to add fertilizer balls or root tabs to the substrate. If you have filled your tank with plants that grow fast, have some aerial roots, are epiphytic (plants that attach to surfaces and are not planted) or float, and your stocking is light to moderate, then liquid or powdered fertilizers may be of assistance.

Every aquarium is unique, so it is advisable to watch your plants over the course of the first month or two and look for signs of deficiency. Generally, this will be in the form of nitrogen, iron, potassium, or trace element deficiency. Signs such as slow growth, thin, spindly leaves and stems, yellowing leaves, pale veins, etc., will indicate that a supplement is required.

While there are many recipes for dosing nutrients, for most basic setups with hardy plants, a liquid fertilizer made by a reputable company will perform well. When selecting a good liquid fertilizer, look for a supplement with trace elements such as iron, manganese, boron, zinc, etc., and one that has a good ratio of nitrogen (N), phosphorus (P), and potassium (K), otherwise known as the NPK ratio. Ideally, a ratio of N with one to two times the K and minimal or zero P is advisable. Plants do require P, but excess can lead to algal blooms and there is usually sufficient P in the aquarium from fish waste and fish food to fulfill the requirements of most plants.

Plants use nutrients continuously just like CO₂, and a regular serving of liquid fertilizer will benefit most tanks. Dosing can be done daily, though every few days or once a week will also suffice. Due to evaporation of water, some elements of fertilizer not used can build up over time, so regular moderate water changes (20 to 40 percent weekly or every other week) are advised when using fertilizers to prevent any dangerous nutrient accumulation. Regular water changes also replenish other elements, such as dissolved minerals (calcium, magnesium) and carbonate salts in the water, and are a necessity for fish.

Now that you have an idea of the basics necessary to set up a planted aquarium, you might be wondering about aquascaping the tank. Next month, I will offer aquascaping tips, a selection of plants that are appropriate for beginners, a how-to guide for placing hardscape items, and more to make your tank look as good as a pro’s.