All aquatic plants have the same basic requirements, which are outlined below, although some are easier to grow than others. There are some plants that you can grow with just the basic requirements, ie water, light, and nutrients (many of which are provided by wastes from the fish) but for others, or for the most luxurious plant growth, you will need to provide extra care, additional lighting, or better fertilization.
The main requirements of plants are:
Plants need a thicker layer of gravel (5 to 10cm) than is used in the average aquarium and fine-grade gravel: around 3mm is best. Gravels that are slightly rounded are better than those which are very sharp-edged. The substrate can be improved by mixing in laterite when the tank is being set up, or by adding laterite balls to an established aquarium. Laterite provides extra iron, which will benefit many plants, especially red plants, crypts, and swords.
If you are serious about setting up a fully planted aquarium, then you should consider undergravel heating. Undergravel heating provides convection currents through the gravel, which serve to replenish nutrients and oxygen for optimum plant health and growth. There are two forms available: low voltage, low wattage models which are relatively inexpensive but which do not take the place of normal aquarium heaters, and high powered models which are also capable of heating the tank, but which can cost several hundred dollars.
Contrary to some reports, some plants can be grown successfully in tanks with undergravel filtration, although others do not like the stronger flow of water past their roots. However, due to other drawbacks, this is not generally the recommended filter system, for example, laterite fertilization cannot be used where undergravel filtration is in place. Plants may also restrict water flow through the undergravel and so reduce its filtration capability.
PROPER AQUARIUM LIGHTING
All plants require light to grow, and aquatic plants need a very specific spectrum and a reasonably high light intensity. Some very hardy plants (eg thin and giant Vallis) can survive at quite low light levels, but most plants require that at least one proper aquarium fluorescent tube (eg Aquaglo or Powerglo) is used. These proper aquarium tubes provide the correct spectrum for aquatic plants, that is, plenty of red and blue wavelengths, but not too much yellow. A twin fitting (or more) is even better, and reflective inserts can also be used to increase the light directed into the aquarium.
Even better lighting systems are Compact fluorescent and Mercury Vapour, which, although more expensive than a single normal fluorescent is of comparable cost to using multiple fluorescent tubes. Compact fluorescents in particular are very popular because they are cool running and economical, and provide about twice the light of normal fluorescents. If hanging lighting is prefered, mercury vapour gives a cheaper alternative to Metal Halide and offers a pleasant natural-looking light. Metal Halide lighting is used by very serious hobbyists: this is the best lighting but has a very high initial cost and higher ongoing costs.
Ideally, the lights should be put on a timer, and run for 10 to 12 hours per day. Running lighting longer than this (regardless of the type used) will only promote the growth of algae. It should be noted that you cannot make up for insufficient light intensity by running the lights longer.
Plants need the right combination of light intensity and duration, and it is also true that running overly intense lighting for a short period is more beneficial to algae than to desirable plants.
Therefore, you should tailor your lighting to suit the requirements of the types of the number of plants you have. Use more lighting for those varieties that need it, or where your tank is heavily planted. However, if you are growing varieties without high light requirements or if you have just a few plants, you will not want too much light or again, it will be algae that benefit.
Household or other fluoro tubes are not recommended, as these tend to have a more yellow spectrum. This not only makes the aquarium look murky but also encourages algae to grow rather than your desirable plants. Too much sunlight is also not recommended. In natural waterways, much of the yellow portion of sunlight is absorbed, but this does not occur in aquaria, with the result that algae use this excess light to grow. Direct sunlight can also cause overheating of the aquarium.
OPTIMUM NUTRIENT BALANCE
All plants, both land-based and aquatic, use light to create energy from carbon dioxide and water and to fuel their growth. In order to grow, they also need other nutrients. In aquarium water is obviously readily available, but other nutrients may be lacking.
Apart from carbon dioxide, the main nutrients required by aquatic plants are Nitrogen and Phosphorus. Both of these major nutrients are usually in ample (or over) supply in the aquarium since they are present in the waste products of the fish: nitrogen from ammonia and nitrate from fishes wastes and phosphates from dry fish food. Calcium, iron and magnesium are also needed, and these are often found in tap water. Other nutrients of importance are potassium and manganese, and plants also need minute amounts of boron, copper, zinc and other trace elements.
Some plants do not require additional fertilization and will grow simply by utilizing these major nutrients that are already in the aquarium. However, even hardy plants need these nutrients in a certain balance. An over-or under-supply of even a single nutrient can lead to poor plant growth and tip the balance in favor of the algae. Regular water changes will remove excess nutrients and replenish some of those that are in short supply.
Despite the fact that most important nutrients are present, many plants will still not grow without the addition of essential trace elements, or extra iron or other nutrients, and fertilization is certainly needed in order to achieve really beautiful, lush, plant growth. This is because the lack of a single nutrient or trace element can retard the growth of plants.
Fertilizers for aquatic plants are available in a number of forms, each designed to complement the others by targeting a different group of plant needs. Firstly there are iron-rich fertilizers such as laterite which are placed into the gravel. Many plants, especially those with red in the leaves, require a high iron content, and they take this up through their roots. Secondly there are tablet or liquid base fertilizers which provide all the basic nutrients for growth, excepting nitrogen and phosphorus. These are added periodically and replenished after water changes. And finally there are trace elements, added daily in liquid form. Trace elements are needed only in minute quantities, but they are unstable in water and so must be replenished often.
In general, adding any one type of fertilizer will be beneficial, but you will only get the best effect by using a combination. For the overall best growth, these different fertilizers should be used in conjunction to ensure a perfect balance of nutrients.
In no case should garden fertilizer be used! Fertilizers for garden plants are high in nitrogen and phosphorus and will lead to an oversupply of these nutrients. This will not only promote algae growth but excess nitrate and phosphate are also detrimental to fish and plants.
Carbon dioxide (CO2) is the staple food of plants. In the aquarium, CO2 is present due to respiration from fish and the decay of organic matter, but the supply of CO2 is not usually enough to support a well-planted aquarium. This is not to say the plants will not survive without CO2, but by adding CO2 faster plant growth, and more luxurious, better-developed plants can be achieved. However, adding extra CO2 will only be of benefit if the lighting is sufficient and the supply of other nutrients adequate. Remember that the lack of anyone important factor, whether it is light, water (for land plants), nutrients, or CO2, will limit the growth and development of plants.
A range of kits for adding CO2 is available, from quite basic and inexpensive models which generate and inject CO2 as well as more sophisticated units which run from a depot and give more control over CO2 injection, right up to fully computer-controlled systems. If carbon dioxide is added, carbonate hardness should be monitored to be sure this stays above 4 KH (80 mg/L). Otherwise, the CO2 can cause pH to drop.
Carbon dioxide will be removed by vigorous aeration of the water, so this should be avoided in planted tanks, at least during daylight hours. Once the lights have been turned off, the supply of CO2 should be reduced or stopped as plants only utilize CO2 while they are photosynthesizing, ie while the lights are on. When the lights are off, plants respire and produce carbon dioxide. Alternatively, an air pump can be run while lights are off to disperse excess carbon dioxide.
SUITABLE FISH & ALGAE EATERS
There is little point in going to great lengths to promote plant growth if the aquarium is filled with plant-eating fishes, as these can consume plants as quickly as they grow. Some fish are strict herbivores and will eat nearly any type of plant, while others are more general feeders that will nibble on the plants that they find appetizing while leaving others alone. If you are keeping strictly herbivorous fish such as scats, silver dollars, and other large characins, there is nothing that can be done to stop them from eating plants. Goldfish are another group of well-known plant-destroyers, although some tough-leaved plants can be encouraged to grow in goldfish aquariums. One trick is to feed goldfish a large number of small feeds throughout the day. If they are constantly expecting flakes or pellets or frozen foods, they are more likely to disregard the plants. The same method can be used with some plant-eating cichlids.
Other fish cannot be mixed in a well-planted aquarium not because they eat the plants, but because they either dig or behave in a boisterous manner that leads to damage to or uprooting of the plants. Such fish include large cichlids and catfish.
Fortunately, most common tropical community fish can be kept in planted aquariums. Nearly all tetras, live-bearers, rasboras, sharks, barbs, rainbows, and gouramis are suitable, along with most small catfish and a number of cichlids. Aside from goldfish, most coldwater fish (eg danios) are also plant-friendly.
Algae eaters are desirable in any aquarium, but especially in planted aquariums. Algae use the same nutrients as plants and will flourish where these are even slightly out of balance. Algae eating fish will help to control any algal growth that does occur. The best species are bristlenose catfish, siamese foxes, and otocinclus catfish. These are effective algae eaters that do not damage plants. Some large algae eaters (eg Plecostomus) may damage leaves while they are rasping at algae. Other algae eaters who help but may not be able to control algae on their own are mollies, shark species, whiptail catfish & small freshwater shrimp.
GOOD WATER QUALITY
Just like fish, plants do not like extremes of pH or temperature or poor water quality. Most plants are happiest at a pH around neutral (ie between 6.5 and 7.5), and at normal tropical temperatures, ie 24 to 26°C. Heating is not required for many types, except in very cold climates, but some varieties will start to suffer at below 20°C. Conversely, many plants do not like prolonged temperatures above 28°C.
Regular partial water changes are important to keep pH stable (by replenishing carbonate hardness and removing acid wastes) and to remove excess nutrients (particularly nitrate and phosphate). Good water clarity is also important, since sediment in the water will clog the leaves of fine-leaved plants. Therefore, the best filtration for planted aquariums should combine biological filtration and mechanical filtration. Canisters are the most highly recommended filter, although overflow and internal power filters can also be used, particularly in smaller aquaria.
CONTROL OF ALGAE
As mentioned, algae have the same requirements as plants: ie light, nutrients, and carbon dioxide, but can grow and out-compete plants when conditions are not optimal. Therefore, it is important to provide correct lighting and fertilization and to maintain good water quality. Water changes in particular are important, as nitrate is used more readily as a nutrient by algae than by plants.
It is also important to have the tank well planted right from the beginning, using a mix of faster and slower growing plants. If plants are well established soon after the tank is set up, then there is less opportunity for algae to grow. Since it is impossible to prevent all algae growth, algae-eating fishes should also be amongst the first fish introduced in a well-planted aquarium. Make sure you do not feed them too much or they may stop scavenging for algae.
If any algae growth is noticed, perform a water change and remove as much of the algae as possible to prevent the algae from taking hold. If algae are growing on the leaves of the plants it is best to remove the affected leaves rather than trying to clean them. When the tank is new, floating plants can help by mopping up nutrients and shading out algae. If algae do take hold a series of water changes may be needed, and some plants may need to be sacrificed in order to bring it under control. However, with good tank maintenance, this should not occur.
The use of algicides is not recommended except as a last resort, as these can damage the plants. If algae cannot be controlled in other ways, a liquid algicide can be used in conjunction with water changes and the physical removal of algae. After the algae have been controlled, remove any damaged plant leaves, and make sure conditions are optimal for plants.
To conclude, you need knowledge in these aspects to keep live plants in an aquarium?
- Suitable substrate
- Proper aquarium lighting
- Optimum nutrient balance
- Carbon dioxide
- Suitable fish population (including algae eaters)
- Good water quality
It should be noted that algae are a type of plant and so the factors which determine plant growth are also those that influence the growth of algae. Algae however are opportunistic and can grow where conditions are not optimal for plants. If plants are provided with a good environment for growth they will often out-compete the algae, but if the conditions are not perfect, the growth of algae will be promoted instead.