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1. What is Hydroponics?
Hydroponics, simply stated, is the growing of plants without soil.

2.Where can I grow with the hydroponic method?
Anywhere. Indoors, in a greenhouse as well as outdoors. Any plant can be grown with hydroponics, though some are more delicate than others. If there is enough light for the plant to grow, you can probably bet somebody has grown it using hydroponics.

3.What is Aeroponics?
Aeroponics is a method of growing in which oxygen is infused into the nutrient solution, allowing the roots to absorb nutrients faster and more easily. This facilitates rapid growth resulting in fantastic yields.

4.Is hydroponics organic?
There is a huge popular debate about the value of "organic" fertilizers and methods. Many people would like to apply "organics" to hydroponics. Currently accepted organic fertilizer components are dependent upon organisms in the soil to convert the "organic" materials into a useable form for plants. In hydroponics we provide the minerals required for plant growth directly, completely eliminating the need for soil and soil organisms. The result is much higher growth rates and yields, and better crop quality than organic methods can achieve.

5.Why is growing with hydroponics better then growing in soil?
Hydroponic produce is cleaner than its soil grown counterpart, and the grower has the ability to adjust the nutrient feed for maximal growth and yield in the shortest time.

6.How does the taste of hydroponic produce compare with soil grown produce?
Hydroponic produce frequently exceeds soil grown produce in terms of flavor and nutrition. This is because all of the nutrients required by the plant are immediately available when the plant needs them.

7.What is the best system for starting cuttings?
Our CAP root shooters does an excellent job for starting cuttings.

8.Which is the best system for growing smaller plants?
You can use any of our systems, though the AeroFlo produces the most rapid and dramatic results.

9.What is the best system for growing tomatoes, peppers and cucumbers?
These plants have longer growing periods and need enough space for adequate root development. Our best systems for these crops are the Farm Series, PowerGrowers and the Dutch Pots.

10.Can you recommend a simple solution for keeping growing media out of drains?
General Hydroponics' PolyWool was designed for this purpose. It also retains moisture. It is recommended for moisture loving plants, especially in very hot and dry environments.

11.How do I deal with algae build up in my hydroponic system?
The best method is prevention. If you keep the solution away from light, i.e. keep the lids closed and all openings sealed, you can prevent algae from growing. If you already have algae in the system you can remove it with a brush, or use hydrogen peroxide (3ml of 3% H2O2 per gallon of solution) to remove it. If there are particles floating in the nutrient solution, be sure to flush the reservoir and growing chamber with ample water, and then start with a new batch of nutrient. If the problem is severe, make sure you have the algae completely flushed out to avoid the risk of clogging some of the flow lines in the system. HID Lighting Negative resistance and why you need a ballast to limit current In a high-pressure lamp, if current increases, the arc gets hotter. This tremendously increases the concentration of ions and free electrons, making the arc that much more conductive. The conductivity of the arc increases enough that the voltage across the arc usually stays about the same or even decreases if the current is increased. In a low-pressure lamp, a variation of this causes the same thing. If you double the current, you usually roughly double the concentration of excited gas atoms and free electrons. The concentration of ions must match that of free electrons but each excited atom is bombarded twice as much by free electrons (remember, there are twice as many electrons around for an excited atom to see). The average kinetic energy of the free electrons must decrease so that ion concentration is also only roughly doubled. To get slower free electrons, the electric field in the discharge (and voltage across the discharge) must decrease. In either case, it is not a good idea to connect the lamp directly to a voltage source. Once the lamp starts conducting, increasing current will increase the lamp's conductivity, allowing more current to flow. This process does not level off until one of the following happens:

  • A large fraction of easily ionizable atoms are ionized,
  • The concentration of ions/free electrons is so high that more of these somehowimpairs mobility of free electrons,
  • The power supply's or wiring's limitations limit the current.

At this point, the current is usually around or over 100 amps or so, and will likely blow fuses/pop breakers, and is certainly not good for the lamp. The term "negative resistance" refers to a decrease in voltage across the lamp resulting from an increase in current through the lamp.



12.Why the light from many discharge lamps makes red things look dull?
Mercury lamps, most metal halide lamps, most sodium lamps, and "cool white", "white", and "warm white" fluorescent lamps have a shortage of red and green light in their spectral output. These lamps also have a surplus of yellow and/or orange-yellow. Since red plus green looks yellow, taking away red and green and adding yellow do not affect how the lamp's color looks. Nearly all yellow objects reflect red, orange, yellow, and green. Increasing yellow output and decreasing red and green does not change how yellow objects look. However, red objects generally reflect mostly just red light. With the shortage of red light, these look darker. If they are not pure red in color, they will not only look darker but also less red in color. Unphosphored (clear bulb) high pressure mercury lamps are especially bad at this, since they make very nearly no red light at all. This is not a problem with most compact fluorescent lamps, most 1-inch diameter 4-foot lamps, and other fluorescent lamps that have "rare-earth" phosphors. These phosphors, unlike those in older formula fluorescent lamps, produce a strong, narrow orangish red spectral band and a strong, somewhat narrow, slightly yellowish green one, with little in between. Under these lamps, reds usually look near normal, or slightly orangish, or slightly excessively bright. Greens often also look slightly brighter under these lamps than under old formula "cool white" and "warm white" fluorescent lamps. Why photos taken under discharge lamps often look blue-green? The problem here is the fact that film and human eyes have different spectral response. Human eyes are quite sensitive to the short wave end of the red range of the visible spectrum, but not to the long wave end. Most color film responds about the same to shorter and longer red wavelengths. Most of the red light from fluorescent lamps, metal halide lamps, sodium lamps, and phosphored mercury lamps is of shorter red wavelengths. These lamps do not emit much of the longer red wavelengths. This maximizes red sensation by the eye for a given amount of actual light. Producing less-visible longer red wavelengths detracts from maximizing luminous efficacy of the lamp, so this is minimized. Therefore, lamps make a surplus of red wavelengths to which the eye is more sensitive than film is, and a shortage of the red wavelengths to which film is more sensitive than human eyes. This results in the film seeing red less than human eyes do, and this makes photos look blue-greenish. Arc and glow discharges explained! Electrons normally don't just move or flow from a conductor into a gas. Something has to make this happen. Explained below are ways for this to happen. In a glow discharge, positive ions bombarding the cathode dislodge electrons from the cathode material. There is a substantial electric field near the cathode that accelerates ions toward the cathode to make this happen. The whole process tends to complicate itself, resulting in a double layer of glow around the cathode, thin dark spaces underneath and between these layers, and a more substantial dark space between all of this and either the anode or the main body of the discharge, whichever comes first. In neon glow lamps, the anode is so nearby that no main discharge body occurs. "Neon" signs are longer, so a main discharge body occurs. Since these operate on AC, each end has a significant dark space only half the time, so these regions are a bit dim rather than dark. There is generally a natural current density in the cathode process, generally around a milliamp to .1 amp per square centimeter, depending on the gases involved, the pressure thereof, and the cathode material. A glow discharge at this intensity is a "normal glow". Decreasing the current causes the cathode's glowing layers to cover only part of the cathode. In this case, the glow often moves around, causing a flickering effect. If the current is more than enough to cause the cathode to be covered with glow, (or if the glowing layers are forced into a thinner layer of space than they normally use), abnormal glow results. The voltage drop of the cathode process (this voltage is known as the "cathode fall") will be higher than normal. This causes ions to bombard the cathode harder than usual. This increases "sputtering", or dislodging of cathode material atoms. Sputtering effectively "evaporates" cathode material and often causes darkening of the lamp's inner surface. Sputtering occurs more easily at higher cathode temperatures. It is generally recommended to neither have significantly "abnormal" glow nor significant temperature rise in the cathode, and especially not both of these combined. The cathode fall of normal glow is usually 50 to 90 volts for neon, argon, krypton, xenon, or mixtures including significant amounts of any of these gases. Some metal vapors may have somewhat lower cathode falls. Nitrogen and some other gases have high cathode falls usually near or even well over 100 volts. The cathode process in most HID lamps and fluorescent lamps is the thermionic arc. In this process, at the proper high temperature, some material in the cathode fails to keep a grip on its electrons. Therefore, electrons simply flow from the cathode to the gas. The cathode fall is usually around 10 volts, and the heat dissipated in this process keeps the cathode hot enough to let electrons flow from it to the gas. The current density at the cathode process of a thermionic arc is generally in the tens or hundreds of amps per square centimeter of active cathode surface, but can occaisionally be as low as around an amp per square centimeter if a heat source other than the arc heats the cathode. Another arc process is the cold cathode arc. In this process, ions bombard the cathode material and dislodge electrons from it. This seems similar to the glow discharge, but the effect is quite different. The current density in the cathode process is usually hundreds or thousands of amps per square centimeter. The cathode fall is usually near the ionization potential of the cathode material or the main active gas ingredient, whichever is lower (for a minimum) to twice whichever is higher (for a maximum). Substantial sputtering may occur, especially if the cathode is hot. Cold tungsten is usually reasonably tolerant of this, permitting the use of this process in xenon flashtubes. An arc is often not entirely thermionic nor cold-cathode, but one of these processes is usually dominant. If a hot-cathode lamp is underpowered, the cathode is not as able to emit electrons by the thermionic process, and significant cold-cathode arc process may occur. This can cause excessive sputtering. Starting a hot-cathode lamp also results in some of this as the cathode warms up. Overpowering a hot-cathode lamp can simply overheat the cathodes. Because of this, it is generally advised to start fluorescent and HID lamps as infrequently as practical and to neither overpower nor underpower them. This makes it difficult to dim fluorescent and HID lamps significantly without being hard on their cathodes. There are some special dimming ballasts for some fluorescent lamps. These dissipate power into the cathodes to maintain a workable thermionic process when these lamps are dimmed. It is recommended to only dim fluorescent lamps with appropriate ballasts, and to use these dimming ballasts only with the lamps they were designed to safely dim. What do high-pressure sodium lamps have? One thing these lamps have is a mixture of mercury and sodium, rather than just sodium. If only sodium was in these, the voltage across the lamp would be excessively low. Making the arc tube longer to increase voltage drop would also increase the watt-per-centimeter loss (explained below in section 8). A higher sodium vapor pressure would also increase the voltage drop, but would broaden the sodium's emission band to the point that much of the spectral output is nearly infrared. This detracts from maximum most-visible light output. Also, a mercury-sodium mixture conducts heat less than pure sodium vapor. This reduces thermal conduction of energy away from the arc (The watt-per-centimeter loss). Another thing: Hot sodium is very highly chemically reactive. Some of the sodium is lost as the lamp ages, either permeating through the arc tube or chemically becoming part of it. Therefore, a surplus of sodium is included in the arc tube. The sodium vapor pressure is controlled by the temperature of the "amalgam reservoir(s)" of the arc tube, where any unevaporated mercury and sodium reside. Proper lamp operation depends on the amalgam reservoir(s) being at or near a proper temperature. Why do aging sodium lamps sometimes cycle repeatedly on and off? The sodium vapor pressure is controlled by the temperature of the amalgam reservoirs at the ends of the arc tube. As the lamp ages, the ends of the arc tube get darkened, and they absorb light. This makes them hotter. Therefore, the amalgam reservoirs get hotter. This increases the sodium vapor pressure in the arc tube, leading to different electrical characteristics. When this effect becomes excessive, the arc in the arc tube goes out. The arc tube must cool before the vapor in it is thin enough to restrike an arc. Aging sodium lamps sometimes repeatedly turn on and off as the ends of the arc tubes overheat, then cool off once the arc goes out. If a high pressure sodium lamp repeatedly turns on and off, replacing the bulb with a new one is usually all that is needed. Thermal Conduction from High Pressure Arcs, the Watt per Centimeter Loss When energy is dissipated into an arc, it largely leaves the arc by three mechanisms: 1. Some is used by the cathode and anode fall mechanisms getting electrons from metal to arc and vice versa. Nearly all of the energy here ends up heating the electrodes. The anode fall is not always significant, the cathode fall usually is. 2. Thermal conduction removes energy from the main body of the arc. This ends up heating the arc's surroundings and any container or arc tube. 3. Whatever energy enters the body of the arc (not lost in electrode falls) and not thermally conducted from the arc is radiated. Of course, it is desirable to minimize (1) and (2) and to maximize (3). The electrode falls are generally a fairly constant voltage. Designing the main body of the arc to have more voltage across it (higher voltage drop) and use less current reduces the electrode losses. However, there is a limit to practical arc voltages, since higher voltages may require complicated equipment to supply them, and also higher pressure. The thermal conduction loss is a major loss in many high intensity discharge lamps, especially ones of lower wattages. This loss varies with arc temperature, gas and vapor type, and is largely linearly proportional to the length of the arc. However, this loss usually does not vary much with the arc's diameter nor with the gas pressure. Often, especially in mercury vapor lamps, the arc temperature is surprisingly constant, and this leads to a surprisingly constant thermal conduction loss from the arc, in watts per centimeter of arc length. This loss increases if the arc tube size and/or gas pressure are great enough for convection to be significant, and the nearly constant degree of this loss applies to typical general purpose HID arcs that are many times longer than they are wide. The loss is different for the nearly spherical arcs in some special HID lamps. For typical mercury vapor lamps, the thermal conduction loss is generally around 10 watts per centimeter. For high pressure sodium lamps, this loss is less constant but generally near 10 watts per centimeter. This loss can vary with the ratios of the mercury-sodium mix since sodium vapor conducts heat more than mercury vapor does. For metal halide lamps, this loss is less constant and generally greater (in watts per cm.) due to convection in the short, wide arc tubes that are filled to a very high pressure. The watt/cm. loss could be reduced by: A. Using a shorter arc. This requires a higher pressure for the same arc voltage. Also, the parts of the arc tube within one tube radius of the electrodes are subjected to being darkened by evaporated/sputtered electrode material, so it may not pay to have an arc length shorter than a few times the arc tube diameter. Reducing the arc tube diameter would help this, but a skinnier arc tube will get hotter from the same watts of heat per centimeter. All of this combined impairs the design of economical miniaturized HID lamps. B. Fill the arc tube with a less thermally conductive material. Such materials have larger and/or heavier molecules. Heavier molecules move more slowly, larger size ones don't go as far between collisions. This favors use of mercury and xenon as HID lamp ingredients. Low-heat-conductivity gases and vapors should be gaseous at reasonable arc tube temperatures, chemically stable or inert at all temperatures from below freezing to the arc temperature, and not have major infrared or ultraviolet emission lines that detract from efficiently radiating visible light. This largely disqualifies polyatomic substances and the vapors of heavier alkali metals. How important is water quality? Water containing too much calcium and magnesium (called "total Hardness") may create serious problems. Contact your municipal water supplier who can provide you with an analysis of your water supply. If you are using well water, there are many laboratories that can provide you with an analysis if you send them a sample. If the dissolved salts in your water supply measure 200 ppm or more, we strongly recommend that you obtain a water analysis to determine calcium content. Excessive calcium is the main factor in determining if your water is hard. If an analysis of your water supply reveals that the Calcium content of your water supply is greater than 70 ppm (mg/liter) you should use Hardwater FloraMicro. Hardwater FloraMicro provides rapidly growing plants with a combination of chelated micronutrients uniquely formulated for hardwater conditions. Other options are to collect rainwater, install a reverse osmosis filtration system, or use purified water. Do not use mineral or "spring" water, which can unbalance the nutrient solution, or even be toxic to plants. My water is chlorinated, is this a problem? Chlorine is highly volatile, it evaporates as soon as it hits the air. By the time the nutrient solution reaches the roots, the chlorine is gone. I understand the roots also need oxygen. How do they get it? In a properly functioning hydroponic unit, the roots receive oxygen from the air which surrounds them, as well as from the oxygen which is dissolved in the nutrient solution. The proper medium can play an important role in this process.

13.Why photos taken under discharge lamps often look blue-green??
The problem here is the fact that film and human eyes have different spectral response. Human eyes are quite sensitive to the short wave end of the red range of the visible spectrum, but not to the long wave end. Most color film responds about the same to shorter and longer red wavelengths. Most of the red light from fluorescent lamps, metal halide lamps, sodium lamps, and phosphored mercury lamps is of shorter red wavelengths. These lamps do not emit much of the longer red wavelengths. This maximizes red sensation by the eye for a given amount of actual light. Producing less-visible longer red wavelengths detracts from maximizing luminous efficacy of the lamp, so this is minimized. Therefore, lamps make a surplus of red wavelengths to which the eye is more sensitive than film is, and a shortage of the red wavelengths to which film is more sensitive than human eyes. This results in the film seeing red less than human eyes do, and this makes photos look blue-greenish. Arc and glow discharges explained! Electrons normally don't just move or flow from a conductor into a gas. Something has to make this happen. Explained below are ways for this to happen. In a glow discharge, positive ions bombarding the cathode dislodge electrons from the cathode material. There is a substantial electric field near the cathode that accelerates ions toward the cathode to make this happen. The whole process tends to complicate itself, resulting in a double layer of glow around the cathode, thin dark spaces underneath and between these layers, and a more substantial dark space between all of this and either the anode or the main body of the discharge, whichever comes first. In neon glow lamps, the anode is so nearby that no main discharge body occurs. "Neon" signs are longer, so a main discharge body occurs. Since these operate on AC, each end has a significant dark space only half the time, so these regions are a bit dim rather than dark. There is generally a natural current density in the cathode process, generally around a milliamp to .1 amp per square centimeter, depending on the gases involved, the pressure thereof, and the cathode material. A glow discharge at this intensity is a "normal glow". Decreasing the current causes the cathode's glowing layers to cover only part of the cathode. In this case, the glow often moves around, causing a flickering effect. If the current is more than enough to cause the cathode to be covered with glow, (or if the glowing layers are forced into a thinner layer of space than they normally use), abnormal glow results. The voltage drop of the cathode process (this voltage is known as the "cathode fall") will be higher than normal. This causes ions to bombard the cathode harder than usual. This increases "sputtering", or dislodging of cathode material atoms. Sputtering effectively "evaporates" cathode material and often causes darkening of the lamp's inner surface. Sputtering occurs more easily at higher cathode temperatures. It is generally recommended to neither have significantly "abnormal" glow nor significant temperature rise in the cathode, and especially not both of these combined.

The cathode fall of normal glow is usually 50 to 90 volts for neon, argon, krypton, xenon, or mixtures including significant amounts of any of these gases. Some metal vapors may have somewhat lower cathode falls. Nitrogen and some other gases have high cathode falls usually near or even well over 100 volts. The cathode process in most HID lamps and fluorescent lamps is the thermionic arc. In this process, at the proper high temperature, some material in the cathode fails to keep a grip on its electrons. Therefore, electrons simply flow from the cathode to the gas. The cathode fall is usually around 10 volts, and the heat dissipated in this process keeps the cathode hot enough to let electrons flow from it to the gas. The current density at the cathode process of a thermionic arc is generally in the tens or hundreds of amps per square centimeter of active cathode surface, but can occaisionally be as low as around an amp per square centimeter if a heat source other than the arc heats the cathode. Another arc process is the cold cathode arc. In this process, ions bombard the cathode material and dislodge electrons from it. This seems similar to the glow discharge, but the effect is quite different. The current density in the cathode process is usually hundreds or thousands of amps per square centimeter. The cathode fall is usually near the ionization potential of the cathode material or the main active gas ingredient, whichever is lower (for a minimum) to twice whichever is higher (for a maximum). Substantial sputtering may occur, especially if the cathode is hot. Cold tungsten is usually reasonably tolerant of this, permitting the use of this process in xenon flashtubes. An arc is often not entirely thermionic nor cold-cathode, but one of these processes is usually dominant. If a hot-cathode lamp is underpowered, the cathode is not as able to emit electrons by the thermionic process, and significant cold-cathode arc process may occur. This can cause excessive sputtering. Starting a hot-cathode lamp also results in some of this as the cathode warms up. Overpowering a hot-cathode lamp can simply overheat the cathodes. Because of this, it is generally advised to start fluorescent and HID lamps as infrequently as practical and to neither overpower nor underpower them. This makes it difficult to dim fluorescent and HID lamps significantly without being hard on their cathodes. There are some special dimming ballasts for some fluorescent lamps. These dissipate power into the cathodes to maintain a workable thermionic process when these lamps are dimmed. It is recommended to only dim fluorescent lamps with appropriate ballasts, and to use these dimming ballasts only with the lamps they were designed to safely dim.

14.What do high-pressure sodium lamps have?
One thing these lamps have is a mixture of mercury and sodium, rather than just sodium. If only sodium was in these, the voltage across the lamp would be excessively low. Making the arc tube longer to increase voltage drop would also increase the watt-per-centimeter loss (explained below in section 8). A higher sodium vapor pressure would also increase the voltage drop, but would broaden the sodium's emission band to the point that much of the spectral output is nearly infrared. This detracts from maximum most-visible light output. Also, a mercury-sodium mixture conducts heat less than pure sodium vapor. This reduces thermal conduction of energy away from the arc (The watt-per-centimeter loss). Another thing: Hot sodium is very highly chemically reactive. Some of the sodium is lost as the lamp ages, either permeating through the arc tube or chemically becoming part of it. Therefore, a surplus of sodium is included in the arc tube. The sodium vapor pressure is controlled by the temperature of the "amalgam reservoir(s)" of the arc tube, where any unevaporated mercury and sodium reside. Proper lamp operation depends on the amalgam reservoir(s) being at or near a proper temperature.

15.Why do aging sodium lamps sometimes cycle repeatedly on and off?
The sodium vapor pressure is controlled by the temperature of the amalgam reservoirs at the ends of the arc tube. As the lamp ages, the ends of the arc tube get darkened, and they absorb light. This makes them hotter. Therefore, the amalgam reservoirs get hotter. This increases the sodium vapor pressure in the arc tube, leading to different electrical characteristics. When this effect becomes excessive, the arc in the arc tube goes out. The arc tube must cool before the vapor in it is thin enough to restrike an arc. Aging sodium lamps sometimes repeatedly turn on and off as the ends of the arc tubes overheat, then cool off once the arc goes out. If a high pressure sodium lamp repeatedly turns on and off, replacing the bulb with a new one is usually all that is needed. Thermal Conduction from High Pressure Arcs, the Watt per Centimeter Loss

When energy is dissipated into an arc, it largely leaves the arc by three mechanisms:

1. Some is used by the cathode and anode fall mechanisms getting electrons from metal to arc and vice versa. Nearly all of the energy here ends up heating the electrodes. The anode fall is not always significant, the cathode fall usually is.

2. Thermal conduction removes energy from the main body of the arc. This ends up heating the arc's surroundings and any container or arc tube.

3. Whatever energy enters the body of the arc (not lost in electrode falls) and not thermally conducted from the arc is radiated. Of course, it is desirable to minimize (1) and (2) and to maximize (3).

The electrode falls are generally a fairly constant voltage. Designing the main body of the arc to have more voltage across it (higher voltage drop) and use less current reduces the electrode losses. However, there is a limit to practical arc voltages, since higher voltages may require complicated equipment to supply them, and also higher pressure. The thermal conduction loss is a major loss in many high intensity discharge lamps, especially ones of lower wattages. This loss varies with arc temperature, gas and vapor type, and is largely linearly proportional to the length of the arc. However, this loss usually does not vary much with the arc's diameter nor with the gas pressure. Often, especially in mercury vapor lamps, the arc temperature is surprisingly constant, and this leads to a surprisingly constant thermal conduction loss from the arc, in watts per centimeter of arc length. This loss increases if the arc tube size and/or gas pressure are great enough for convection to be significant, and the nearly constant degree of this loss applies to typical general purpose HID arcs that are many times longer than they are wide. The loss is different for the nearly spherical arcs in some special HID lamps. For typical mercury vapor lamps, the thermal conduction loss is generally around 10 watts per centimeter. For high pressure sodium lamps, this loss is less constant but generally near 10 watts per centimeter. This loss can vary with the ratios of the mercury-sodium mix since sodium vapor conducts heat more than mercury vapor does. For metal halide lamps, this loss is less constant and generally greater (in watts per cm.) due to convection in the short, wide arc tubes that are filled to a very high pressure. The watt/cm. loss could be reduced by:

A. Using a shorter arc. This requires a higher pressure for the same arc voltage. Also, the parts of the arc tube within one tube radius of the electrodes are subjected to being darkened by evaporated/sputtered electrode material, so it may not pay to have an arc length shorter than a few times the arc tube diameter. Reducing the arc tube diameter would help this, but a skinnier arc tube will get hotter from the same watts of heat per centimeter. All of this combined impairs the design of economical miniaturized HID lamps.

B. Fill the arc tube with a less thermally conductive material. Such materials have larger and/or heavier molecules. Heavier molecules move more slowly, larger size ones don't go as far between collisions. This favors use of mercury and xenon as HID lamp ingredients. Low-heat-conductivity gases and vapors should be gaseous at reasonable arc tube temperatures, chemically stable or inert at all temperatures from below freezing to the arc temperature, and not have major infrared or ultraviolet emission lines that detract from efficiently radiating visible light. This largely disqualifies polyatomic substances and the vapors of heavier alkali metals.

16.How important is water quality?
Water containing too much calcium and magnesium (called "total Hardness") may create serious problems. Contact your municipal water supplier who can provide you with an analysis of your water supply. If you are using well water, there are many laboratories that can provide you with an analysis if you send them a sample. If the dissolved salts in your water supply measure 200 ppm or more, we strongly recommend that you obtain a water analysis to determine calcium content. Excessive calcium is the main factor in determining if your water is hard. If an analysis of your water supply reveals that the Calcium content of your water supply is greater than 70 ppm (mg/liter) you should use Hardwater FloraMicro. Hardwater FloraMicro provides rapidly growing plants with a combination of chelated micronutrients uniquely formulated for hardwater conditions. Other options are to collect rainwater, install a reverse osmosis filtration system, or use purified water. Do not use mineral or "spring" water, which can unbalance the nutrient solution, or even be toxic to plants.

17.My water is chlorinated, is this a problem?
Chlorine is highly volatile, it evaporates as soon as it hits the air. By the time the nutrient solution reaches the roots, the chlorine is gone.

18.I understand the roots also need oxygen. How do they get it?
In a properly functioning hydroponic unit, the roots receive oxygen from the air which surrounds them, as well as from the oxygen which is dissolved in the nutrient solution. The proper medium can play an important role in this process.

 
 
 
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