Cichlids are a favorite subject to many people all over the world. Some find it an interesting hobby and some find it an easy way to become rich. For many it is a way to bring prosperity. The likes of Flowerhorn cichlids are supposed to be good and powerful Feng Shui symbols. Whatever be the purpose of the people, there are plenty of information about cichlids on the Internet as well as in many books and magazines. But the problem with most of them is that they are not of great quality. So you have to be very careful while selecting a book or magazine to learn more about cichlids.
It is always advisable to have some good exposure to cichlids, as it will definitely improve your skills. Even if you just want to know about cichlids, a quality cichlid book will help you. It is the traditional way to gather information. There may not be images in flash or other video clippings, but information from a book is supposed to be more reliable than any other source. Here are a few publications I would like to recommend, as I am personally familiar with it. The high quality photographs and quality descriptions add to the beauty of these selections. These are only a selection and are published by different publishers.
ponedjeljak, 27. rujna 2010.
Cichlid Care
There are hundreds of genera of African Cichlids. They differ from one another by appearance as well as their nature and behavior. In this article let us discuss about a few common genera of the African variety of the species. All these are fresh water fish. The main habitats of the African Cichlids are the Victoria, Tanganyika and Malawi lakes. But there are other places too, like the delta region of the River Niger where some varieties are found. These three great African lakes have a high alkaline content, having a pH value of 7.0 to 9.0 in their waters. It will be ideal for the water for the tanks where African Cichlids are to be raised to have a pH value over 8.00.
The Calvus group of the African Cichlids is found in three colors, the Black Calvus, the White Calvus and the Yellow Calvus. The Black Calvus requires very hard water with a pH value from 8.5 to 9. The ideal temperature is 25 to 26 degree Celsius. They are carnivorous and the natural habitat is rocky shallow waters. It grows up to 15 centimeters. It spawns in the substrate material. It is only slightly aggressive.
The White Calvus has an attractive slightly reddish color. The Yellow Calvus has black and white stripes along the breadth of the body. There are yellow spots all over the body. Though the color is different all the three, black, white and the yellow, are of the same in size, shape, food habits, water quality requirements, temperament and habitat. All of them spawn in the substrate soil. All of these are sleek in body shape which enables them to have passage through narrow edifices. That helps them to catch their prey.
The Red Fin has mild manners. The temperament is peaceful. It has a grayish black body. The females and the young ones have red fins. They are found naturally in the rocky shore line of the Lake Malawi. The water should be hard and have a temperature between 25 and 28 degree Celsius. The preferred pH value of water is 7.8 to 8.6. This variety prefers rocks for habitat. A grown up Red Fin will have a length of 20 cm. Being a big fish very big tanks are required by them. Perhaps, the Red Fin is the fastest growing cichlid. During courtship males are slightly aggressive. In eating habits they are carnivorous. The Red Fins are mouth brooders. The female carries the spawn in her mouth and release them after 12 to 18 days. The fry do not return to their mother afterwards.
The Mloto Ivory Head is another cichlid found naturally in Tanganyika Lake. This cichlid has an ivory white blaze from the lip to the dorsal fin. It is blue in color and a fully grown Ivory Head measures up to 15 cm. They are carnivorous and peaceful in temperament. Water temperature in the tank must be between 25 and 28 degree Celsius and pH value 7.8 to 8.6. The Mloto Ivory Heads are a maternal mouth brooder African cichlid.
The Calvus group of the African Cichlids is found in three colors, the Black Calvus, the White Calvus and the Yellow Calvus. The Black Calvus requires very hard water with a pH value from 8.5 to 9. The ideal temperature is 25 to 26 degree Celsius. They are carnivorous and the natural habitat is rocky shallow waters. It grows up to 15 centimeters. It spawns in the substrate material. It is only slightly aggressive.
The White Calvus has an attractive slightly reddish color. The Yellow Calvus has black and white stripes along the breadth of the body. There are yellow spots all over the body. Though the color is different all the three, black, white and the yellow, are of the same in size, shape, food habits, water quality requirements, temperament and habitat. All of them spawn in the substrate soil. All of these are sleek in body shape which enables them to have passage through narrow edifices. That helps them to catch their prey.
The Red Fin has mild manners. The temperament is peaceful. It has a grayish black body. The females and the young ones have red fins. They are found naturally in the rocky shore line of the Lake Malawi. The water should be hard and have a temperature between 25 and 28 degree Celsius. The preferred pH value of water is 7.8 to 8.6. This variety prefers rocks for habitat. A grown up Red Fin will have a length of 20 cm. Being a big fish very big tanks are required by them. Perhaps, the Red Fin is the fastest growing cichlid. During courtship males are slightly aggressive. In eating habits they are carnivorous. The Red Fins are mouth brooders. The female carries the spawn in her mouth and release them after 12 to 18 days. The fry do not return to their mother afterwards.
The Mloto Ivory Head is another cichlid found naturally in Tanganyika Lake. This cichlid has an ivory white blaze from the lip to the dorsal fin. It is blue in color and a fully grown Ivory Head measures up to 15 cm. They are carnivorous and peaceful in temperament. Water temperature in the tank must be between 25 and 28 degree Celsius and pH value 7.8 to 8.6. The Mloto Ivory Heads are a maternal mouth brooder African cichlid.
četvrtak, 23. rujna 2010.
Reef Aquarium Lightning
Among the most important aspects of reef keeping is the lighting system. With lighting, we want to provide the proper photoperiod, intensity, and spectrum for good coral and anemone growth. Most applications use a 12-hour photoperiod. With multi-light systems, you can use timers to vary the intensity by varying the number of lights on at any one time. Usually, one bulb comes on for an hour, then all bulbs for 10 hours, and then one light is left on for an additional hour while the others are turned off. This is one method to duplicate the sun passing over the reef. On really elaborate systems, some hobbyists have even designed cloud cover patterns.
To provide proper light intensity, use 3-5 watts per gallon and use multiple fluorescent lights if the tank is 30" deep or less. Deeper tanks require more elaborate systems, usually involving hanging metal halide pendant lighting. Most books suggest one 175-watt metal halide per 4 square feet of surface area, hanging about 1 foot above the tank.
The development of electronic ballasts for Very High Output (VHO) fluorescent lighting, has allowed enthusiasts to design high wattage systems in small spaces. A 48" VHO bulb outputs 110W, versus 40W for a standard bulb. VHO systems require special end caps to withstand the higher heat emitted. Most of these tubes are available with internal reflectors to maximize intensity. Use bulbs with a CRI of 90-99 (CRI 100=sunlight), or color temperature of 5500-10,000K.
Most corals have light intensities at which they grow best. This is important to know when selecting bulbs and determining at what depth a certain coral should be placed. Most corals are a little forgiving as light intensity goes. It is important, though, not to "blind" new coral when placing them in the tank, as this can lead to light shock or bleaching of the zooxanthellae. Place new corals deeper in the tank than the optimum and provide some shading. Once acclimated, (generally about 2 weeks), raise them to the optimal level.
Choosing the right bulbs: Variety of bulbs to provide zooxanthellae with the proper wavelengths of light for photosynthesis, different bulbs have been developed to mimic sunlight filtered through different depths of water. As light penetrates water, different wavelengths with different "energies" will penetrate to varying depths. Red light (630-780 nm) penetrates to about 15 m, while blue light (420-490 nm) goes as deep as 250 m. So, it is not surprising that most zooxanthellae have evolved to absorb light best at 420 nm in the blue range. This has led to development of fluorescent bulbs that emit light primarily at this peak: Actinic 03-type bulbs. While you could use all actinic lighting on a reef, you may find the result disappointing. (Our eyes do not perceive blue light as very bright, and find yellow light more aesthetically pleasing.) Also recommended are "full spectrum" bulbs, "tuned" to produce light across the full spectrum, mimicking natural sunlight. These tubes show the true colors of corals and fish, and are pleasing to our eyes. Most reefs work best with a 1:1 ratio of actinic to full spectrum bulbs. Also available to hobbyists, are combination bulbs often called 50/50 or actinic white; these emit light across the full spectrum, with extra "actinic" phosphors for additional light at 420 nm. Most metal halides have adequate spectrums for reefs, though most hobbyists supplement with actinic 03-type bulbs to bring out corals' red and green fluorescence. Another effect of metal halide use, since they are a single point light source, is that we will get light defraction waves in the tank. While these waves are found in nature and are pleasant to the eye, they have not been shown to be essential to reef keeping.
The size and lighting choices that you make will have a big impact on the success of your reef. While this may appear confusing at first, make sure to take the time to research your options and then choose the ones that will allow your tank to thrive.
To provide proper light intensity, use 3-5 watts per gallon and use multiple fluorescent lights if the tank is 30" deep or less. Deeper tanks require more elaborate systems, usually involving hanging metal halide pendant lighting. Most books suggest one 175-watt metal halide per 4 square feet of surface area, hanging about 1 foot above the tank.
The development of electronic ballasts for Very High Output (VHO) fluorescent lighting, has allowed enthusiasts to design high wattage systems in small spaces. A 48" VHO bulb outputs 110W, versus 40W for a standard bulb. VHO systems require special end caps to withstand the higher heat emitted. Most of these tubes are available with internal reflectors to maximize intensity. Use bulbs with a CRI of 90-99 (CRI 100=sunlight), or color temperature of 5500-10,000K.
Most corals have light intensities at which they grow best. This is important to know when selecting bulbs and determining at what depth a certain coral should be placed. Most corals are a little forgiving as light intensity goes. It is important, though, not to "blind" new coral when placing them in the tank, as this can lead to light shock or bleaching of the zooxanthellae. Place new corals deeper in the tank than the optimum and provide some shading. Once acclimated, (generally about 2 weeks), raise them to the optimal level.
Choosing the right bulbs: Variety of bulbs to provide zooxanthellae with the proper wavelengths of light for photosynthesis, different bulbs have been developed to mimic sunlight filtered through different depths of water. As light penetrates water, different wavelengths with different "energies" will penetrate to varying depths. Red light (630-780 nm) penetrates to about 15 m, while blue light (420-490 nm) goes as deep as 250 m. So, it is not surprising that most zooxanthellae have evolved to absorb light best at 420 nm in the blue range. This has led to development of fluorescent bulbs that emit light primarily at this peak: Actinic 03-type bulbs. While you could use all actinic lighting on a reef, you may find the result disappointing. (Our eyes do not perceive blue light as very bright, and find yellow light more aesthetically pleasing.) Also recommended are "full spectrum" bulbs, "tuned" to produce light across the full spectrum, mimicking natural sunlight. These tubes show the true colors of corals and fish, and are pleasing to our eyes. Most reefs work best with a 1:1 ratio of actinic to full spectrum bulbs. Also available to hobbyists, are combination bulbs often called 50/50 or actinic white; these emit light across the full spectrum, with extra "actinic" phosphors for additional light at 420 nm. Most metal halides have adequate spectrums for reefs, though most hobbyists supplement with actinic 03-type bulbs to bring out corals' red and green fluorescence. Another effect of metal halide use, since they are a single point light source, is that we will get light defraction waves in the tank. While these waves are found in nature and are pleasant to the eye, they have not been shown to be essential to reef keeping.
The size and lighting choices that you make will have a big impact on the success of your reef. While this may appear confusing at first, make sure to take the time to research your options and then choose the ones that will allow your tank to thrive.
ponedjeljak, 20. rujna 2010.
Oscar Cichlid
Enthusiasts planning to raise Oscar Cichlids should prepare a large tank, spacious enough to accommodate the immediate growth of this kind of fish. Oscars tend to grow an inch after its eight to tenth month. Expect them to reach about 10-12 inches on their first year. Gravel is the most recommended substrate for the tanks since they are abundant in the Oscar's natural environment.
However, be sure to make use the rounded kind since these types of fish are inclined to dig, and sharp gravel might harm them. Furthermore, there are observations that these fish do not prefer bright lights. Thus, this should also be considered in preparing their tanks.
Hobbyists who are obsessed with decorated tanks should think twice to raise Oscars since they tend to be disastrous pets, often rearranging their aquarium, moving rocks and decors around. These are normal Oscar behaviors. Let them do this for it increases their comfort zone on their surroundings.
Feeding can be an exciting experience since Oscars interact whenever they are fed. They show excitement, swimming eagerly around the tank when they know they will be fed. They eat insects and small crustaceans such as crickets, earthworms, mealworms and shrimps.
They might just think that their reflections are another fish trying to get in their territories. Oscars, like most cichlids, are territorial. They need to be accustomed to their tank mates for a while before they given in. That is the reason why in some cases, it is suggested that Oscars should be bred early with another type of fish for the former to be accustomed to it while growing.
Breeders should also take note that in most cases, it is hard to distinguish a male from a female Oscars. The only indication of a female Oscar is when it becomes pregnant and begins to be bulkier. They lay their eggs on a surface of a rock, and will rearrange their space to provide a suitable spawning area in their tanks. The eggs hatch after three days.
nedjelja, 19. rujna 2010.
Saltwater Aquarium Plants
Saltwater aquarium plants add color and interest to your marine tanks and form part of any well thought out marine tank. But that''s not all they do. Macroalgae and marine plants will also make the ecosystem in your tank healthier. Macroalgae are particularly beneficial as they provide a natural form of filtration in the saltwater tank.
Saltwater aquarium plants take in nutrients from the water in order to carry out their biological functions and growth. This action reduces the accumulation of toxic nitrates and phosphates and other impurities in the water. When you use plants in your marine tank the idea is to reproduce your fish and other organism''s natural habitat. A tank that contains saltwater aquarium plants is likely to be a healthy one.
Here are some examples of saltwater aquarium plants that you can choose for your marine tank:
Halimeda or cactus algae are hardy saltwater aquarium plants and won''t be fed on vigorously by most marine fish. It is also non-invasive so it won''t damage nearby corals or invertebrates. It does need good light to grow in however as well as enough calcium for growth. Halimeda are sensitive to high nitrate and phosphate levels and don''t like to be pruned.
Penicillus or "shaving brush" are saltwater aquarium plants that do a great job at absorbing excess nutrients like nitrates and phosphates from the water. They are usually not fed on by most fish and invertebrates except sea urchins. Plant the pencillus in the substrate and make sure the area is well-lit. If you add an iron supplement and trace elements regularly your pencillus should thrive. Pencillus has a hard calcium carbonate skeleton like halimeda an coralline algae and will do well across a range of conditions.
What about macroalgae? Macroalgae are saltwater aquarium plants that come in a variety of different shapes and sizes. They are to be found in a range of colors ? red, green, brown and blue. These saltwater aquarium plants are able to photosynthesize. This means they use a pigment called chlorophyll to make their own food for growth and other functions.
In general these saltwater aquarium plants get most of the nutrients they need from the water in the marine tank. These include nitrates and phosphates. This makes them good allies in keeping your tank clean. You will need moderate to strong light for the growth of macroalgae. The way to avoid macroalgae growing out of control is to control the environment in which it lives. This means the water chemistry and amount of available light.
So are there ''bad'' saltwater aquarium plants? Certain kinds of algae can become problematic in a marine tank.
Bubble algae is one of the most common pest saltwater aquarium plants. Bubble algae forms green bubbles on any hard surface, for example live rock. It can occur in masses of bubbles or single or in small groups of big bubbles. The bubbles might be smooth or rough. Bubble algae look nice, BUT they aren''t!
These saltwater aquarium plants grow fast and can take over your tank. Once you discover it the best thing to do is remove it and keep it under control. It can damage other plant species. You can usually remove it by hand. When you do, try not to break the bubbles as this might cause it to spread.
You can try to introduce certain types of fish like the Sohal Tang or Red Sea/Indian Ocean Sailfin Tang (Acanthurus sohal) to eat bubble algae. The best means of control, however, seems to be the "Emerald Crab". These crabs won''t damage your corals but will eat the bubble algae. It is a good idea to learn about other such interactions between saltwater aquarium plants and herbivores as they might save you time and trouble in the future.
The emerald crabs are a great idea for the reef aquarium where they won''t fight with other inhabitants. There are even coral farmers who use emerald crabs to control algae around their hard corals! So you can protect your saltwater aquarium plants by stocking some of these little helpers.
So what''s your next step? Now that you know a little bit about the good and the bad kinds of saltwater aquarium plants, it''s your job to make sure you learn more. Your local aquarist will be able to tell you more about which saltwater aquarium plants are most suitable for your tank, level of expertise and the other species you want to stock.
You can also do more research on the Word Wide Web, visit your local library or buy books on the subject. Don''t ever buy your saltwater aquarium plants on a whim because you like the way they look. Always make sure you know as much about their nutrient, environment and lighting needs as possible. That way you can avoid making mistakes that cost time and money or even threaten the health of your tank in the long term.
Do choose saltwater aquarium plants that you find attractive as this is part and parcel of keeping a marine tank but never let your desires cloud your common sense. Once you have all you plants set up you will be able to enjoy the animal plant interactions that are so much a part of the marine ecosystem. The purpose of any aquarium is to provide both the fish and you with hours of pleasure and enjoyment. A healthy tank is a happy tank so do take the time to do your research.
Saltwater aquarium plants are very beautiful to look at and interesting to grow so make sure that you take the time to enjoy the plants in your tank. Find out if it is possible to propagate any of these plants from, how to increase or decrease their growth and what nutrients they need to stay healthy. Never share plants between aquariums unless you know they are 100% disease free and always put the health of your tank at the top of your list of priorities! Have fun and enjoy your saltwater aquarium plants!
Saltwater aquarium plants take in nutrients from the water in order to carry out their biological functions and growth. This action reduces the accumulation of toxic nitrates and phosphates and other impurities in the water. When you use plants in your marine tank the idea is to reproduce your fish and other organism''s natural habitat. A tank that contains saltwater aquarium plants is likely to be a healthy one.
Here are some examples of saltwater aquarium plants that you can choose for your marine tank:
Halimeda or cactus algae are hardy saltwater aquarium plants and won''t be fed on vigorously by most marine fish. It is also non-invasive so it won''t damage nearby corals or invertebrates. It does need good light to grow in however as well as enough calcium for growth. Halimeda are sensitive to high nitrate and phosphate levels and don''t like to be pruned.
Penicillus or "shaving brush" are saltwater aquarium plants that do a great job at absorbing excess nutrients like nitrates and phosphates from the water. They are usually not fed on by most fish and invertebrates except sea urchins. Plant the pencillus in the substrate and make sure the area is well-lit. If you add an iron supplement and trace elements regularly your pencillus should thrive. Pencillus has a hard calcium carbonate skeleton like halimeda an coralline algae and will do well across a range of conditions.
What about macroalgae? Macroalgae are saltwater aquarium plants that come in a variety of different shapes and sizes. They are to be found in a range of colors ? red, green, brown and blue. These saltwater aquarium plants are able to photosynthesize. This means they use a pigment called chlorophyll to make their own food for growth and other functions.
In general these saltwater aquarium plants get most of the nutrients they need from the water in the marine tank. These include nitrates and phosphates. This makes them good allies in keeping your tank clean. You will need moderate to strong light for the growth of macroalgae. The way to avoid macroalgae growing out of control is to control the environment in which it lives. This means the water chemistry and amount of available light.
So are there ''bad'' saltwater aquarium plants? Certain kinds of algae can become problematic in a marine tank.
Bubble algae is one of the most common pest saltwater aquarium plants. Bubble algae forms green bubbles on any hard surface, for example live rock. It can occur in masses of bubbles or single or in small groups of big bubbles. The bubbles might be smooth or rough. Bubble algae look nice, BUT they aren''t!
These saltwater aquarium plants grow fast and can take over your tank. Once you discover it the best thing to do is remove it and keep it under control. It can damage other plant species. You can usually remove it by hand. When you do, try not to break the bubbles as this might cause it to spread.
You can try to introduce certain types of fish like the Sohal Tang or Red Sea/Indian Ocean Sailfin Tang (Acanthurus sohal) to eat bubble algae. The best means of control, however, seems to be the "Emerald Crab". These crabs won''t damage your corals but will eat the bubble algae. It is a good idea to learn about other such interactions between saltwater aquarium plants and herbivores as they might save you time and trouble in the future.
The emerald crabs are a great idea for the reef aquarium where they won''t fight with other inhabitants. There are even coral farmers who use emerald crabs to control algae around their hard corals! So you can protect your saltwater aquarium plants by stocking some of these little helpers.
So what''s your next step? Now that you know a little bit about the good and the bad kinds of saltwater aquarium plants, it''s your job to make sure you learn more. Your local aquarist will be able to tell you more about which saltwater aquarium plants are most suitable for your tank, level of expertise and the other species you want to stock.
You can also do more research on the Word Wide Web, visit your local library or buy books on the subject. Don''t ever buy your saltwater aquarium plants on a whim because you like the way they look. Always make sure you know as much about their nutrient, environment and lighting needs as possible. That way you can avoid making mistakes that cost time and money or even threaten the health of your tank in the long term.
Do choose saltwater aquarium plants that you find attractive as this is part and parcel of keeping a marine tank but never let your desires cloud your common sense. Once you have all you plants set up you will be able to enjoy the animal plant interactions that are so much a part of the marine ecosystem. The purpose of any aquarium is to provide both the fish and you with hours of pleasure and enjoyment. A healthy tank is a happy tank so do take the time to do your research.
Saltwater aquarium plants are very beautiful to look at and interesting to grow so make sure that you take the time to enjoy the plants in your tank. Find out if it is possible to propagate any of these plants from, how to increase or decrease their growth and what nutrients they need to stay healthy. Never share plants between aquariums unless you know they are 100% disease free and always put the health of your tank at the top of your list of priorities! Have fun and enjoy your saltwater aquarium plants!
Substrate and Fertilization Introduction
Plants need a balance of macro nutrients, (those they use the most of), and minor or trace nutrients, (which they use to a lesser degree).
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The Substrate is the growing medium that the plants are rooted in. It is important to add a source of these nutrients to the substrate, particularly in a new aquarium that has no mulm or fish waste settled in it yet.
It is also advisable to use a medium such as porous gravel that will provide a good CEC and not compact together. CEC, (cation exchange capacity) is the ability of the medium to absorb cation ions, (minerals from fertilizers) and hold them making them accessible to the plants when the plants need them. Sand and coated gravel do not provide a good CEC. Good CEC mediums include porous gravel, clay litter, and clay soils.
Macro nutrients include nitrogen, oxygen, CO2, potassium, phosphorus, calcium. Minor elements include iron, Boron, zinc, manganese, and other trace minerals. Iron is an important element for many plants and is often added to the substrate with other minerals.
Laterite is a sediment soil that is formed in nature by decaying rocks which are high in iron and aluminum. There are a few aquarium products made of laterite, such as Duplarit, and First Layer. Other sources of iron are soils, clay litter, red pottery clay, and sphagnum peat.
Various substrate methods
- Layered substrate with "sub" soil (soil low in organics), sphagnum peat, gravel, and trace element mix, as outlined by Steve Pushak
- Pottery clay balls enhanced with fritted trace elements, as outlined by Steve Pushak, or commercial additives made for the aquarium
- Clay gravel
- Granular laterite, sphagnum peat, and gravel, my mix of choice.
Fail-safe beginner substrates:
- Commercial products, laterite, clay gravel, clay based additives made for the aquarium
NPK What are those three numbers?
Nitrogen supplied by the fish, phosphates by the water supply and uneaten food, and potassium to a lesser degree in the water supply. NPK fertilizers should only be added if you have low or unreadable levels already. RO, distilled, and some bottled spring water will be low in NPK and mineral elements. Most tap water will have sufficient levels of P. Even some aquarium products contain NPK. An NPK fertilizer high in potassium, but low or 0 in nitrate and phosphate is has the least affect on algae. Check the numbers. Single digits are low, double digits are high. In a heavily planted tank with fast growing plants, and a small number of fish, it is possible to have consistent 0 readings of nitrate and phosphate creating a nitrogen and phosphate deficiency for the plants.
Target nutrient ranges
| Nitrate (N03) 5 to 10ppm | Phosphate (PO4) 0.2ppm to 0.5ppm |
| Iron (Fe) 0.2 to 0.7ppm | Potassium (K) 20-30ppm |
Types of fertilizers
| tablets | spikes |
| balls | liquid |
Sources of trace elements
- Soils: Iron (Fe) other trace elements High CEC
- Pottery clay: Iron, (Fe) High CEC
- Clay litter: Iron, (Fe) High CEC
- Vermiculite: trace amounts Iron, Potassium, Magnesium Very High CEC
Drawbacks of Soil substrates
When plants are removed, replanted, the soil mixture can come up with the plants and pollute the water. You are better off using a clay gravel if you anticipate moving and transplanting plants often.
The Following information is taken from "Something to Grow on", Cornell University. It is not written specifically for aquariums, but the information is very useful. I particularly like the information on CEC.
Ions Cation exchange capacity
(CEC) Quantifies the ability of media to provide a nutrient reserve for plant uptake. It is the sum of exchangeable cations, or positively charged ions, media can adsorb per unit weight or volume. It is usually measured in milligram equivalents per 100 g or 100 cm3 (meq/100 g or meq/100 cm3, respectively). A high CEC value characterizes media with a high nutrient-holding capacity that can retain nutrients for plant uptake between applications of fertilizer. Media characterized by a high CEC retains nutrients from leaching during irrigation. In addition, a high CEC provides a buffer from abrupt fluctuations in media salinity and pH. Important cations in the cation exchange complex in order of adsorption strength include calcium (Ca2+) > magnesium (Mg2+) > potassium (K+) > ammonium (NH4+), and sodium (Na+). Micronutrients which also are adsorbed to media particles include iron (Fe2+ and Fe3+), manganese (Mn2+), zinc (Zn2+), and copper (Cu2+). The cations bind loosely to negatively charged sites on media particles until they are released into the liquid phase of the media. Once they are released into the media solution, cations are absorbed by plant roots or exchanged for other cations held on the media particles. Anion exchange capacity Some media retains small quantities of anions, negatively charged ions, in addition to cations. However, anion exchange capacities are usually negligible, allowing anions such as nitrate (NO3-), chloride (Cl-), sulphate (SO4-), and phosphate (H2PO4-) to leach from the media.
Cation Exchange Capacities for various growing media amendments and selected media.
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| Sources: see Bunt, A.C. 1988, and Landis, T. D. 1990. |
Sphagnum peat moss
Sphagnum peat moss, derived from the genus Sphagnum, contains at least 90% organic matter on a dry weight basis. In addition, this peat moss contains a minimum of 75% Sphagnum fiber, consisting of recognizable cells of leaves and stems. Approximately 25 species of Sphagnum exist in Alberta, Canada and 335 species are present throughout the world. Sphagnum fuscum is an important species bearing many desirable traits. Sphagnum grows in northern cool regions and is also located in peat bogs found in Washington, Maine, Minnesota, and Michigan. Many pores are present in the leaves of sphagnum; when used as growing media, as much as 93% of the water occupying this internal pore space is available for plant uptake (Peck, 1984). After draining, sphagnum peat can hold 59% water and 25% air by volume. Sphagnum is usually characterized by an acidic pH, low soluble salts content, structural integrity, and the ability to serve as a nutrient reserve (Landis, 1990). Although peat mosses are classified into four different groups, variation may exist within any one type of peat moss. Peats of the same classification often differ notably in quality, and even peats from the same bog taken from separate layers can possess different chemical and physical properties.
Sphagnum peat moss is classified as light or dark peat, based on its color. Light peats are characterized by a large amount of internal pore space, 15-40% of the pore space comprises aeration porosity Dark sphagnum peat does not display the elasticity of light peat and is usually not as long lasting.. Dark sphagnum peat moss maintains twice the cation exchange capacity of light peats, yet does not possess as much total or aeration porosity. An associated table lists general characteristics of sphagnum peat moss.
Inorganic media
Materials such as vermiculite, perlite, and sand represent the inorganic fraction often used in container media formulations. These materials generally increase the aeration porosity and drainage yet decrease the water-holding porosity of media. Inorganic components are usually inert materials characterized by a low cation exchange capacity.
Vermiculite
Vermiculite is a commonly used inorganic media component which is mined in the U.S. and Africa. This mineral, comprised of an aluminum/iron/magnesium/silicate mixture, is excavated as a material composed of thin layers. Processing includes heating the vermiculite to temperatures upwards of 1000ƒC, which converts water trapped between the layers of the material into steam. The production of steam results in a pressure that expands the material, increasing the volume of the pieces 15 to 20 times their original size. Vermiculite is sterile because of these high heating temperatures used during processing. Vermiculite is characterized by a high water-holding capacity as a result of its large surface area: volume ratio, a low bulk density, nearly neutral pH, and a high cation exchange capacity attributed to its platy structure. Because it compacts readily when combined with heavier materials, vermiculite is sometimes recommended more for propagating material than container media.
Vermiculite gradually releases nutrients for plant absorption; on average it contains 5-8% available potassium and 9-12% magnesium. This inorganic media component can adsorb phosphate--some of which remains in an available form for plant uptake--but cannot adsorb nitrate, chloride, or sulfate. Vermiculite can fix ammonium into a form that is not readily available for plant absorption. This fixed nitrogen is gradually transformed to nitrate by microorganisms, making it available for plant uptake.
Vermiculite is manufactured in four different grades, differentiated by particle size. Insulation grade vermiculite and that which is marketed for poultry litter (which has not been treated with water repellents) has been used with some success. Vermiculite which has been treated with water repellent, such as block fill should not be used as growing media. Because vermiculite tends to compact over time, it should be incorporated with other materials such as peat or perlite to maintain sufficient porosity. It should not be used in conjunction with sand or as the sole media component, because as the internal structure of vermiculite deteriorates, air porosity and drainage decreases (Landis, 1990).
The particle size of vermiculite influences the water-holding and aeration porosity of the material. Although grade classification is based upon particle size, each grade is represented by a range of particle sizes. Note that grades consisting of larger particle sizes have a higher aeration porosity and lower water-holding porosity than grades consisting of a smaller range of particle sizes. Properties of the four vermiculite grades are shown in an associated table.
Perlite
A mineral of volcanic derivation, perlite is a second inorganic component which may be used in formulating container mixes. This chemically inert material is extracted in New Zealand, the U.S., and other countries and is usually mined by scraping the earth's surface. The processing method includes a grinding and heat treatment (up to 1000‰C) which results in very lightweight, white sterile fragments. As the ore is heated, internal water escapes as steam, resulting in the expansion of the material.
Perlite has a very low cation exchange capacity, low water-holding capacity (19%), and neutral pH. The closed-cell composition of perlite contributes to its compaction resistance, enhances media drainage, and heightens the aeration porosity of peat-based media (Bilderback 1982). Because perlite contains only minute amounts of plant nutrients, liquid feeding is a practical mode of fertilization. Be aware of possible aluminum toxicity in acidic media (pH < 5).
The very low levels of fluoride perlite contains is not likely to pose plant health problems. Any soluble fluoride present in a media characterized by 6.0 < pH < 6.5 will precipitate out of the media with excess calcium from sources such as gypsum, limestone, or calcium nitrate.
Although perlite has several positive attributes, it also has drawbacks. Perlite consists of many fine fragments which, when dry, can lead to lung or eye irritation. In addition, because water clings to the surface of perlite, it may tend to float in the presence of water (Landis, 1990).
Perlite contains, on average, 47.5% oxygen, 33.8% silicon, 7.2% aluminum, 3.5% potassium, 3.4% sodium, 3.0% bound water, 0.6% iron and calcium, and 0.2% magnesium and trace elements (Perlite Institute, 1983). Although a uniform categorization of perlite does not exist, individual producers of this inorganic component assign grade levels. Perlite classifications for horticultural use are listed in an associated table. This inorganic media amendment is sometimes recommended for use only in propagation media because of its low bulk density and tendency to compact.
In comparison with sand, polystyrene, or pumice, perlite has the greatest inner total porosity. Coarse perlite is characterized by approximately 70% total porosity, 60% of which is aeration porosity. Perlite can retain two to four times its dry weight in water, which is much greater than that of sand and polystyrene, yet much less than the water-holding capacity of peat and vermiculite (Moore, 1987).
Sand
Sand has been used as an inorganic media component to add ballast to containers. Some sands contain calcium carbonate which may raise media pH undesirably. A rise in pH may lead to nutrient deficiencies, particularly of minor elements such as iron and boron. A few drops of dilute hydrochloric acid or strong vinegar may be added to sand to test for carbonates; if bubbling and fizzing result, carbonate is present as a result of carbon dioxide production. Sand used for container media should have a 6 < pH < 7. Sand maintains good drainage, a low water-holding capacity, and a high bulk density when used independently of other materials. Because of its shape and size, sand can obstruct pore spaces, decreasing drainage and aeration, instead of improving porosity. Various sand particle sizes have been recommended for container media use, including ranges of 2-3 mm or 0.05 - 0.5 mm (fine sand) in size (Landis, 1990). In addition, another recommendation suggests that 60% of the particles be within 0.25-1.0 mm range, and 97% be greater than 0.1 mm and less than 2 mm (Swanson, 1989). Uniformity coefficients assigned to sand mixtures signify the amount of sand which is within a certain size range; a coefficient < 4 is evidence of a homogeneous sand mixture (Swanson, 1989). If the correct grade of sand is used, the wet ability of the media is enhanced.
Calcined clays
When fired at high temperatures, some clays, fuel ash, and shales form stable compounds that possess low bulk densities and internal porosities of 40-50%. Though calcined clays alter the physical attributes of media in a positive way, they also decrease the level of water-soluble phosphorus in the mix. Because calcined clays are characterized by a high cation exchange capacity, fertilizer application rates may need to be modified if calcined aggregates are incorporated into the media mixes (Bunt, 1988).
Pumice
Pumice is produced as volcanic lava cools; escaping steam and gas contribute to its porous nature. This alumino-silicate material contains potassium, sodium, magnesium, calcium, and slight amounts of iron. Pumice can absorb K, Mg, P, and Ca from the soil solution and render it available for plant absorption later (Bunt, 1988).
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