Copyright 2001 by George and Karla Booth
Why is it that discus seem so magical? Perhaps it's because they have the reputation as being difficult fish to keep and are only worthy of the most experienced aquarists or maybe it is their regal demeanor. After all, they are often described as "King of the Aquarium". Anyone who has seen a magnificent breeding pair will have to agree it's a sight to behold. If you have ever had the chance to browse some of the discus books on the market, you will realize that few fish can create an impression like discus, and a school of them in a large tank is simply awesome.
As aquatic plant enthusiasts, we naturally gravitate towards spectacular aquariums. A large, carefully aquascaped display can hold us spell-bound for hours. Many aquatic gardeners have wondered about combining discus and live plants. Would the combination be as remarkable as the pairing of peanut butter and chocolate? Mr. Takashi Amano, the author "Nature Aquarium World", certainly seems to think so - some of the most impressive photos in his books are of planted discus tanks. Followers of the recent Aquatic Gardeners Association Aquascaping contest noted that quite a few of the entries featured discus in an aquatic garden.
But is a planted discus tank as simple as dropping a Hershey bar into a jar of Skippy peanut butter? If you are guessing "Not Exactly", you are right. But it is not as difficult as you might imagine. We have successfully maintained planted discus tanks for 15 years. This article is based on our experiences and hopefully will give you the knowledge and confidence needed to create your own spectacular discus habitat.
There are several advantages to keeping discus in a planted aquarium. The most obvious advantage is the sheer beauty of this combination. Discus tend to be slow moving and graceful fish and look perfectly at home amid plants slowly swaying in the current. Their coloration, especially the metallic turquoise variants, is a perfect match to the natural greens and reds of live plants. And, especially important to us aging aquatic gardeners, discus are big fish and are easier to see from the sofa compared to the more typical tetras found in our displays!
On a more serious note, plants are known to act as chemical filters to help remove toxic substances from the water. This is a very important attribute for a discus tank. Discus are sensitive to water quality and they place more of a demand on the aquarist to maintain high standards. A good collection of healthy plants will lead to a healthy overall environment and will help stave off common diseases like "hole-in-the-head".
Plants also provide natural hiding places for discus. Discus tend to be shy fish and are sometimes bothered by activity outside the tank. Plants are preferred to other tank decorations since a large discus can easily hurt itself on a piece of driftwood or large rock. Providing a stress-free environment will also promote good health in your discus.
Broad-leafed plants make nice spawning sites for a breeding pair of discus. While most breeders prefer a breeding cone or piece of slate, our discus have often spawned on Anubias or Echinodorus leaves. Plant leaves make good spawning sites in a community tank since the other leaves on the plants help shield the spawning pair from other inhabitants as well as nosy aquarists.
There are some disadvantages you should consider before you take the plunge with discus. They are warm-water fish and typically are kept in water over 80 degrees Fahrenheit. For example, we have always kept ours at 82 F. The higher temperature will limit to some degree the species of plants that will do well. We'll discuss this in more detail later.
All the discus books recommend feeding discus very well to maximize their growth and to get them in top condition for breeding. Some breeders offer four or five feedings per day of high protein food like beef-heart mixtures. The fish have a period of time to eat the food, then the remaining food is vacuumed from the tank to avoid water quality problems. Partial water changes are done frequently to keep nitrates very low. Anyone who has maintained a plant tank realizes that trying to clean up uneaten food and doing lots of water changes is difficult.
With a planted discus tank, a compromise must be achieved . We feed high quality food once per day and do large water changes every other week. This keeps nitrates fairly low (less than 15 mg/l) but doesn't allow the fish to get as big as possible. Our fish tend to grow to seven or eight inches in diameter instead of the ten to twelve inches we have seen in some breeders tanks. The smaller size seems to scale better to the 100-gallon tanks we use, so we don't see this as a problem. Also, even though we are not trying to breed them, they do spawn regularly so the reduced rations don't seem to crimp their sex drive.
Lastly, a planted discus tank should be arranged with plants that don't require frequent trimming. Some discus tend to be shy and spook easily, so the less time you spend digging around in the tank, the better off they are, and the better they will look. Even the most even-tempered discus will sometimes freak out and thrash around the tank, possibly injuring themselves on driftwood or equipment.
Over the years, the aquatic gardening community has developed many "best practices". A few of these practices need to be compromised to have a successful planted discus tank.
The most common practice seen in planted tanks is the use of higher intensity lighting to promote fast plant growth and to accommodate "light loving" plants. The common rule of thumb of "2 to 3 watts per gallon" is often used as the starting point. Many aquarists mistakenly think "more is better" and brag of setups using VHO or metal halide bulbs generating 4 or 5 watts per gallon. In general, plants don't need this much light and this kind of intensity might very well scare the discus into hiding most of the time.
We have been very successful with 1.5 to 2 watts per gallon on our planted tanks. The actual bulbs you use will greatly influence the amount of light intensity you achieve with any specific wattage. We use high efficiency tri-phosphor bulbs and end up with about 15,000 Lux at the water surface. This intensity produces excellent growth and doesn't seem to bother the discus.
The type of lighting may be important. Our very first discus tank used two metal halide (MH) bulbs suspended above the water. These bulbs create well-defined point sources of light that produce rippling shadows in the tank from ripples on the water surface. The discus in this tank seemed shyer than in tanks with fluorescent bulbs. We don't know if it was the shadows, the high intensity point sources or just coincidence. The average brightness at the surface was also 15,000 Lux.
Another best practice is to achieve an "aged" substrate. Mulm and detritus collect in a planted tank and many aquatic gardeners leave it there, allowing it to break down and recycle nutrients. This will generally lead to higher nitrates in the water column. This is to be discouraged since discus like a cleaner environment and higher water quality than less demanding fish. It is recommended that light gravel vacuuming be done during water changes to keep excess waste material at a minimum.
Everyone knows that good water circulation is beneficial to plants. To put it simply, plants can't chase after food like fish can and must depend on the water currents to bring nutrients to the leaves and remove waste products. Good circulation also improves growth by reducing the boundary layer at the leaf/water interface allowing CO2 to be absorbed more quickly. Although it would be difficult to simulate the flow of a river in an enclosed tank, some aquarists strive to do just that by using multiple filters and powerheads to move water.
Fast moving water in a discus tank in not recommended. Discus tend to be slow movers and have a big "sail" area due to their round bodies. If faced with a high current situation, they would expend a lot of energy maintaining their position. They are also slow feeders and might have trouble getting at food being blown rapidly past them in the currents.
This is not say that a discus tank should be stagnant. Some water circulation is needed to keep the water oxygenated properly and to allow filtration to do its job. Some strong currents are fine if the discus have some relatively quiet areas to hang out. In fact, plants with large leaves like Echinodorus can provide both "wind breaks" and attractive hiding places.
One of the goals of many aquatic gardeners is to have a "dense planting". They aren't satisfied until every square millimeter of the aquarium substrate is planted. The sight of bare gravel is an abomination to them. Likewise, the water column itself doesn't look right unless it is solid plant material. These aquascaping techniques don't work well for a planted discus tank for two reasons. First, discus are primarily bottom feeders and like to leisurely pick at food lying on the bottom. If the food settles down into a mass of plants, the fish won't be able to get to it and water quality problems will result. Secondly, discus are big fish and need room to swim. Obviously, if the tank is solid plants, they won't have much swimming room. Let's add a third reason - if the tank is densely planted and you can't see the discus, you've missed the whole point of the exercise!
The last thing to consider is the selection of tank mates for the discus, especially in the area of algae eaters. Algae eaters are important in a plant tank but should be selected carefully. Again, discus are big and slow moving and have a tasty slime coat. They make great targets for sucker mouth algae eaters! Always avoid aggressive algae eaters like "Chinese Algae Eaters" (Gyrinocheilus aymonieri).
You should also be on the alert for other types known to be more benign. For example, Otocinclus are generally peaceful algae eaters and are readily available. However, there are many varieties of otos and the particular species is usually not tracked by the local fish store (unless you are very lucky). We have had trouble only one time - a group of otos we tried once turned out to be "attack otos" and just loved to latch onto the sides of the discus, leaving round white areas when the discus finally shook them off. We have also had minor problems with some Farlowella acus - they also found the discus attractive. Luckily, the farlies aren't very good at swimming and the discus could easily avoid the oddly wiggling stick moving towards them.
The very popular "Siamese Algae Eater" (Siamensis crossocheilus) is very useful in a plant tank but may cause problems with discus. Siamese Algae Eaters are very fast swimmers and, likewise, very fast eaters that may out-compete the discus for food. However, we have always kept them with discus and have not had any problems. They will definitely grab for any food offered, but don't seem to eat that much even when full grown. There is still plenty of food left for the discus.
On the same note, be careful when choosing other fish to keep with discus. Don't choose fast swimmers that may startle the discus and don't choose fast eaters that will eat their food. One of the best and most complementary fish is the Cardinal Tetra (Paracheirodon axelrodi). A good strategy is to introduce cardinals when the discus are still juveniles and let them grow up together. Otherwise, the small cardinals usually found in fish shops may become a very expensive dinner for full-grown discus.
Another nice fish to keep with discus is a school of Corydoras. Bottom feeders will help keep uneaten food from becoming a problem and corys are everyone's favorite. They do best in schools, so get a half dozen of one of the smaller species like C. trilineatus to act as your groundskeepers.
A fish to avoid is the common angelfish (Pterophyllum scalare). They are known to carry parasites harmless to themselves but fatal to discus and, like most other cichlids, are fast eaters.
Discus are widely known to prefer soft, acidic water. In nature, the Amazon black-water biotope is extremely soft, rather murky and has a low pH. However, since the discus you have are probably far removed from the Amazon, the environment you design for your discus should actually match the environment in which they were raised. This means contacting the discus breeder, if possible, to determine the conditions to which your fish are accustomed.
Another factor determining your set up is whether you desire to breed the fish or display them. Breeding will demand a closer match to an "optimum" set of water parameters; a display tank will require less stringent needs. If you are not trying to optimize for breeding, the best idea is to select conditions you can easily achieve when changing water to provide a stable environment. It is far better to settle for harder, more alkaline water than to have to struggle with elaborate water softening and pH adjusting equipment and chemicals.
One mistake many beginning discus keepers make is to use too small of a tank. Most young discus are sold when they are quarter- or half-dollar size. It is easy to assume that six or eight would fit nicely in a 20-gallon tank. Nothing could be further from the truth. Breeders recommend about 40 gallons as the minimum size for a pair; I would extend this rule to display tanks also. We have kept four to six adults in a 100-gallon tank and that seems just about right. It is important to consider both volume and scale - a taller tank (24") is preferred to a lower, longer tank since discus are round. An 8" discus is much taller than a typical 8" fish!
One idea is to start with a larger number of juvenile discus than you intend to keep and cull the weaker or less attractive fish as necessary. We have found that in any batch of juveniles, some will be dominant and some will be submissive. In our experience, the submissive fish will die off, either because they don't eat well or are picked on by the others. If your local fish shop takes trades, you may be able to give some of the young discus back (they may do well in another tank where they may become the dominant fish).
We are lucky to have very soft water directly from the tap. Our water comes from mountain reservoirs and is primarily snow melt. It averages about 0.5 to 1 degree General Hardness (GH or calcium/magnesium hardness). This level of calcium hardness may be fine for a discus-only tank but we feel it is too low for good plant growth. We add calcium carbonate to boost the GH to about 2 degrees. In our 100-gallon discus tank, this works out to about 4 teaspoons (8 grams) of reagent grade CaCO3.
|Note: For reference, two teaspoons (about 4 grams) of calcium carbonate per 50 gallons of water will increase both General Hardness (GH) and Carbonate Hardness (KH) by approximately 1 degree. One teaspoon (about 6 grams) of sodium bicarbonate per 50 gallons of water will increase KH by about 1 degree and will not increase GH. Always use a test kit to determine if you are adding enough hardening agents - it is very difficult to get accurate measures of dry chemicals without sensitive laboratory scales. With most common aquarium test kits, 1 degree of hardness (dGH or dKH) is equivalent to 17.8 mg/l of CaCO3, the standard for measuring hardness.|
Even though discus are thought to prefer lower pH values, we like to keep our display tanks around pH 6.9. For us, this means adjusting KH and CO2 levels to achieve the desired pH. In a non-planted situation, various commercial pH-adjusting compounds could be used to adjust pH. However, these usually contain phosphates and will lead to algae problems in a planted tank with higher lighting and nutrient levels.
To set the pH, we add sodium bicarbonate (NaHCO3, common baking soda) to increase the KH of our tap water from 2 degrees up to 4 degrees (the equivalent of about 70 mg/l CaCO3). Note that the calcium carbonate added earlier to increase GH will also increase KH; always check KH after increasing GH to see how much sodium bicarbonate you need to add. In our case we add 2 teaspoons (12 grams) of reagent grade NaHCO3 to get a final value of 4 dKH.
|Note: Most KH test kits actually measure total alkalinity. If carbonate is the only buffer in the water, total alkalinity equals carbonate hardness. If there are other buffers in the water, such as phosphates, you will not get a true KH reading from a KH test kit. Plan accordingly.|
The second part of the pH equation is CO2. When KH is increased, pH will also increase. To bring the pH back to where we want it and to provide plants with enough CO2 to grow well, we inject CO2 to achieve a concentration of 15 mg/l. That concentration of CO2 and 4 dKH will set the pH at 6.9. There are many copies of the KH/CO2/pH tables available on the Internet so you can juggle the KH and CO2 to suit your own requirements. We recommend that you do not exceed a CO2 concentration of more than 15-20 mg/l with discus.
We prefer to use a pH controller that measures pH in the tank and turns on or off a solenoid to control the flow of CO2. With care, you can use a manually controlled CO2 system to do the same thing. After getting the KH to the right level, simply adjust the CO2 flow until the tank has the pH that you desire.
Higher Temperature Water
Aquarists have found that discus have better disease resistance at higher temperatures and will set the water temperature anywhere between 80 F and 86 F (27 C to 30 C) or higher. We find that algae seems more problematical at higher temperatures and we like to stay towards the lower end of this scale - about 82 F.
One positive aspect of higher temperature is that undergravel heating coils are not such a problem as they are at lower temperatures. Aquarists who don't live in air conditioned houses find that aquarium temperatures in summer months get into the 80 F range and thwart the use of undergravel heating coils - extra heat is not needed and the cables sit idle.
Due to higher water temperatures, there is less oxygen capacity in the discus tank. At sea level, oxygen saturation in water at 75 F is 8.4 mg/l; at 86 F it is down to 7.6 mg/l. This is even more critical if you are at higher elevations - the combination of high altitude (we are at 5000 feet) and warmer water further reduces oxygen levels. A planted tank is very useful for discus since the plants can supersaturate the water during the day, pushing oxygen levels to 120% of saturation or more. We will typically see O2 levels of 8.3 mg/l in the evening - equivalent to cool water at sea level.
As a further safety measure, we use trickle filters to ensure that water stays well oxygenated even at night when the lights are off and plants stop photosynthesizing. We note that that oxygen levels are about 90% in the morning before the lights come back on. This same level can be achieved by running airstones at night but at the expense of dramatic CO2 loss.
A final aspect of a planted discus tank is the selection of plants that are low maintenance. The less you are digging around in the tank, the happier the discus will be! Low maintenance will generally mean slower growing; avoid some of more common stem plants like Hygrophila and Ludwigia .
First time discus keepers are often concerned about the plants they can use in a discus tank. The main concerns are usually soft water and higher temperatures. We have found that there is really no problem with growing plants in these conditions (with a few exceptions). We feel that the size, shape and maintenance requirements of the plants used are more important.
An obvious choice of plants for a discus tank is the Echinodorus family. They are native to the Amazon basin although they might not be found to a great extent in the black water areas favored by discus. Echinodorus come in many sizes and shapes and can be used to great effect in discus tanks.
For a centerpiece plant, it is hard to beat a healthy Amazon Sword (Echinodorus bleheri). The large graceful leaves, the bright green color and the lovely fountain shape make this a classic large-aquarium plant. It works well with discus because its scale is just about right - leaves can grow to 24" or more and it can occupy a fairly large area of the tank. Discus can easily hide among the leaves. The size and shape of the leaves make them suitable for spawning sites, although discus may prefer a more solid surface.
Other sword plants suitable for the main focus of the tank are E. amazonicus, E. major, E. cordifolius and their many variants. A very popular and attractive variant is the Ozelot sword developed by Tropica in Denmark.
Echinodorus include many plants that are perfect for accent or foreground plants. There are a variety of dwarf chain swords that are prefect for foregrounds. The very popular E. tenellus has a grass-like appearance and is easy to grow. Larger varieties like E. quadricostatus and E. latifolius make a nice transition between foreground and centerpiece plants.
The Anubias family represents a large collection of plants from Africa. Although not indigenous to the discus biotope, they are very useful as background and accent plants. They contrast nicely with Echinodorus since they tend to be a darker green and have a different leaf shape. They are also very sturdy plants that provide good spawning sites.
Anubias are good for almost any type of aquarium, as they are very undemanding. They will tolerate low light levels, but they really thrive with higher light and CO2. It is not uncommon to see them sprout underwater flowers frequently under optimum conditions. They do better in harder water but we have had no problems with them in our set ups.
The easiest to find are the Anubias barteri variants. Anubias barteri tends to be a big plant with horizontal leaves up to 6" long. The nana variety is a smaller plant that is good for fore- or mid-ground detail. A rarer variant known as A. coffeeafolia has deeply incised leaves and is very attractive in the mid-ground.
There are other types of Anubias, such as A. afzelli and A. congensis, that are more suited for taller tanks. These tend to have vertical petioles and leaves and look much like sword plants. These are also good candidates for discus tanks but may not do as well in soft, warm water.
Taller, thinner plants
Other plants useful in a discus tank are those that have a taller form factor to keep a strong vertical theme in the aquascaping. Also keep in mind contrast and textures.
Members of the Crytocoryne family, especially C. wendtii and C. blassi, are very nice accent plants with their strong vertical shapes and dark colors. There are many variants of C. wendtii, so you can find a range of pleasing leaf shapes and sizes to suit foreground uses. We have not noticed any problems with crypts in soft, warmer water.
The two members of the Ammania family, A. gracilus and A. senegalensis, work very well in a discus tank. They are not extremely fast growers and make a very attractive red accent plant. They can be propagated by pruning and replanting the top and allowing new shoots to develop at the cut in the remaining stem.
Some members of the Bacopa family are cool water plants and may not be suitable for a discus tank. However, we have used B. monnieri in our tanks as both an accent plant and as background plants. It is a fairly slow grower and has a nice bright green color.
We have also had good luck with the following plants in discus tanks:
- Java Fern, Microsorum pteropus
- Micranthemum family
- Hydrocotyle family
Less Useful Plants
There are some plants that are just not recommended for the discus tank. Many of the plants native to
North America are adapted to cooler water and may not do well. We have experimented with the
following plants and found them to be intolerant of warmer water:
- Samolus parviflorus
- Amoracia aquatica
- Bacopa caroliniana
Other very common aquatic plants are either fast growers or produce dense foliage and may require too
much pruning. These would be useful for getting a general plant tank started but should be removed later
on for a discus tank:
- Hygrophila family
- Ludwigia family
- Rotala family
- Large Vallisneria family (unless kept under control)
Plants and Romance
Are plants compatible with breeding discus? The final answer is - Yes and No. In some ways, plants are very good for a breeding tank. A nice arrangement will allow a breeding pair to set up and defend a territory. This in itself is a strong plus factor. And the better water quality usually seen in a planted tank is also beneficial. We have many discus pair up and begin spawning in our display tanks. One time we even had two pairs spawning at the same time on opposite ends of a 100-gallon tank.
But there are enough drawbacks to make a planted tank less than ideal for breeding discus. We think the biggest obstacle is the inability to provide the maximum amount of food required to grow the breeding pair to a robust size and maintain them in best breeding condition. Discus breeders like to feed large amounts of high protein food such as beef heart mixtures. If any uneaten food like this is left in the tank, problems will surely arise. This is best done in a bare tank set up for breeding purposes.
Even though we have had many pairs spawn in our display tanks, none of the fry have gotten very far past the free-swimming stage. Our display tanks are community tanks with other discus and fish such as cardinal tetras and algae eaters. The parents do a great job of defending the eggs and the very young fry but just can't keep track of a large school of little ones zipping around the tank.
Our advice would be to use a display tank for the purpose of raising young discus to breeding size and then set up a special purpose breeding tank when some of them pair off and begin to breed.
George and Karla Booth have been planted tank enthusiasts since 1970. They set up their first "modern" planted tank in 1986 when they began using CO2 injection and other innovations introduced in "The Optimum Aquarium" by Horst and Kipper. Since then they have authored numerous articles for the Aquatic Gardeners Association newsletter and various aquarium magazines. They live in Ft. Collins, Colorado.