007
Active Member
This topic is a very widely debated subject. There are many opinions, a few facts, and very little absolutes. This must be kept in mind while deciding which option is best for you.
With that said, there are a few things that must be decided upon before any lighting is purchased as there are different systems available for different types of tanks. As mentioned in previous articles, what you pick depends on what type of tank you want. So lets start there . . .
Fish Only Tanks: If you are planning on setting up a tank that is only going to house fish, then your decision is pretty simple. You can basically get away with anything you want in this type of tank. Since its a fish only tank, and you don't have any photosynthetic animals, there is no need to get expensive or high powered lights. The fish don't care . . . as long as they can see, they're happy! So if this is your tank, then instead of spending a couple hundred on an expensive light set up, go with a standard twin tube fluorescent light strip and spend the money on some really nice fish!
Fish only with live rock: This is pretty much the same as above. If you want the lights, then get em' . . . if not, don't buy em'. You can always upgrade later.
Reef Tanks: This is where it gets challenging. Reef tanks are a whole new ballgame with lights because obviously, most corals are photoysnthetic light loving animals. And since we can't shine the sun in our living room, we improvise!
There are numerous options once again with reef lighting and once again, it depends on what you are trying to achieve with your tank and what types of corals you would like to keep. To get things started, lets go over the various options available, and from there we can talk about which lights are best for which kinds of corals.
Some basic terminology:
Watts: The amount of electricity used to power the bulb. It is NOT - I repeat NOT - the output of the bulb. There is a direct relationship between power consumption and output, but Watts are NOT a measure of output. They measure input. This is one of the reasons why WATTS PER GALLON IS A USELESS RULE! Do not use it! (I'll expand on this in a minute)
Lumens: A lumen is a unit of measurement of light and is equal to one foot-candle falling on one square foot of area. The more lumens, the brighter the bulb. Lumens indicate how bright an object is to human eyes, but it is not a unit of light output, its just how bright it is. The difference is subtle but important.
PAR: Photosynthetically available radiation - It indicates the total energy available to plants and corals for photosynthesis, and is thus a key parameter for biological and ecological studies. This is a most important number to pay attention to when deciding on which lights to use. Unfortunately PAR isn't listed so you need to search for someone that has a PAR meter and has published results with the bulb you're interested in. A lot has been done with the common MH bulbs but flourescents are severly lacking.
Kelvin: This is the color of the light that the bulb produces. The acceptable range for reef aquariums ranges from 6500K (yellow) to 20,000K (blue). So the lower this number, the more yellow the light, and the higher the number the more blue. Some people use pure 20K bulbs and their tanks often appear rather blue. Others use a 10K bulb which is a crisp white. This is the most important number to pay attention to when deciding on lights because if you buy a bulb outside of the spectrum useable by corals then you are buying a useless bulb. Another thing to keep in mind is that the higher the K rating, the deeper the light will penetrate in to the water. Hence why the ocean looks blue.
Ballast: The mechanism that converts electricity to a useable energy for the bulb. This is what lights the actual bulb. They are available in a variety of types including electronic and mechanical, normal, HO, VHO, HQI, etc. The ballast you choose must match the type of bulb you use.
Well, thats the basics . . . there is much more, but at least with this info you can get the general idea. Lets start talking about some specifics!
Fluorescent
Normal Output (NO): These lights are the lowest on the totem pole. They are the standard lights that come with aquariums when you buy them. They are really inappropriate for most set ups as they are not powerful enought to sustain corals for long term periods. However, one potential application which may find NO lights appropriate is in a refugium. They can be bright enough to grow algae which is the purpose of a refugium. The only advantage of NO lights are that they are cheap, readily available in a variety of sizes, lengths, and kelvin ratings.
High Output (HO): These are the next step up from NO lights. These lights again are available in a variety of lengths, sizes, and kelvin ratings. These are capable of sustaining some corals for a long time and can be used in some reef aquariums. A relatively new light on the market are the new T5's which are HO lights and have so far established themselves as an acceptable light source. These bulbs require a special ballast to drive them.
Very High Output (VHO): Same as above only even more powerful. These lights are again capable of sustaining a variety of corals longterm. The bulbs are readily available in a number of sizes, kelvin, lengths, etc.
Power compacts (in my opinion) are probably somwhere between HO and VHO. I personally am not a fan of PC's because of their reputation of breaking easily and up until recently they did not have a true actinic bulb available in PC. However they do now apparently.
High Intensity Discharge (HID)
Metal Halide (MH): As of now, these are the cadillac of the lighting world. These are VERY bright lights which are capable of sustaining all types of coral. They come in numerous Kelvin ratings and wattages ranging from 70w up to 1000w. The most commonly used in reef aquariums are 150w, 175w, 250w, and 400w. There are two types of MH lighting, mogul base which are large bulbs that are encased in a Glass housing that screw in to a socket similar to a standard light bulb. Then there are the HQI bulbs which are also known as double ended (DE) halides. These bulbs do not have a glass housing and thus need to be shielded before being used. They snap into a special socket. The HQI bulbs are generally brighter. Using MH bulbs will give a nice shimmering effect in the water where as fluorescents will not . . . a nice benefit in my opinion!
MERCURY VAPOR - The Iwasaki DL Mercury Vapor bulb run on a Mercury Vapor Ballast is about the best bang for the buck out there in terms of PAR per penny. Some report that it grows very healthy corals very quickly but that most SPS grown under the Iwasaki are Brown and the light is fairly yellow.
Lights NOT acceptable for reef tanks:
Halogen
Incandescent
High pressure sodium
The reasons behind this are generally lack of PAR, wrong kelvin, or just plain impracticality.
So lets briefly return to that watts per gallon thing . . .
In addition to the notion that watts measure input, not output, another thing to consider is that as a tank gets deeper, the less light is penetrating the water. For example, if you have a 20 gallon tank that is 5 inches tall (its an example, not reality), and run 100 watts of NO fluorescent lights, thats about 5 watts per gallon. But what if the tank was still a 20 gallon tank and 100 inches tall . . . do you think that its going to be just as bright on the bottom as the 5" deep tank? I hope not . . .
Another thing to consdier is that MH light penetrates the water better than fluorescent light. So 400w of MH does not equal 400w of VHO. In sum . . . the watts per gallon rule is JUNK!
So how about corals? What lights do you need to keep what corals? This is something that is FAR beyond the scope of this thread. It would take a whole book to adequately cover this topic so I will just cover the bare bone basics . . . .
Soft corals (those without a calcerous skeleton) in general require the least amount of light. You can keep a soft coral tank with using all HO lighting.
Large Polyp Stony (LPS) corals require more light than soft corals. They can be kept under HO, but VHO would be better.
Small Polyp Stony (SPS) corals require VERY bright light that is only achieved with MH lights. SPS kept under less than MH will fail to thirive if they even survive. Clams also fall into this category.
I know that there is a LOT more that needs to be covered on this subject. Please feel free to ask questions, make corrections, ask clarification, etc . . .
Like I said, this is a highly debated subject, and I am no expert . . .
Enjoy!
With that said, there are a few things that must be decided upon before any lighting is purchased as there are different systems available for different types of tanks. As mentioned in previous articles, what you pick depends on what type of tank you want. So lets start there . . .
Fish Only Tanks: If you are planning on setting up a tank that is only going to house fish, then your decision is pretty simple. You can basically get away with anything you want in this type of tank. Since its a fish only tank, and you don't have any photosynthetic animals, there is no need to get expensive or high powered lights. The fish don't care . . . as long as they can see, they're happy! So if this is your tank, then instead of spending a couple hundred on an expensive light set up, go with a standard twin tube fluorescent light strip and spend the money on some really nice fish!
Fish only with live rock: This is pretty much the same as above. If you want the lights, then get em' . . . if not, don't buy em'. You can always upgrade later.
Reef Tanks: This is where it gets challenging. Reef tanks are a whole new ballgame with lights because obviously, most corals are photoysnthetic light loving animals. And since we can't shine the sun in our living room, we improvise!
There are numerous options once again with reef lighting and once again, it depends on what you are trying to achieve with your tank and what types of corals you would like to keep. To get things started, lets go over the various options available, and from there we can talk about which lights are best for which kinds of corals.
Some basic terminology:
Watts: The amount of electricity used to power the bulb. It is NOT - I repeat NOT - the output of the bulb. There is a direct relationship between power consumption and output, but Watts are NOT a measure of output. They measure input. This is one of the reasons why WATTS PER GALLON IS A USELESS RULE! Do not use it! (I'll expand on this in a minute)
Lumens: A lumen is a unit of measurement of light and is equal to one foot-candle falling on one square foot of area. The more lumens, the brighter the bulb. Lumens indicate how bright an object is to human eyes, but it is not a unit of light output, its just how bright it is. The difference is subtle but important.
PAR: Photosynthetically available radiation - It indicates the total energy available to plants and corals for photosynthesis, and is thus a key parameter for biological and ecological studies. This is a most important number to pay attention to when deciding on which lights to use. Unfortunately PAR isn't listed so you need to search for someone that has a PAR meter and has published results with the bulb you're interested in. A lot has been done with the common MH bulbs but flourescents are severly lacking.
Kelvin: This is the color of the light that the bulb produces. The acceptable range for reef aquariums ranges from 6500K (yellow) to 20,000K (blue). So the lower this number, the more yellow the light, and the higher the number the more blue. Some people use pure 20K bulbs and their tanks often appear rather blue. Others use a 10K bulb which is a crisp white. This is the most important number to pay attention to when deciding on lights because if you buy a bulb outside of the spectrum useable by corals then you are buying a useless bulb. Another thing to keep in mind is that the higher the K rating, the deeper the light will penetrate in to the water. Hence why the ocean looks blue.
Ballast: The mechanism that converts electricity to a useable energy for the bulb. This is what lights the actual bulb. They are available in a variety of types including electronic and mechanical, normal, HO, VHO, HQI, etc. The ballast you choose must match the type of bulb you use.
Well, thats the basics . . . there is much more, but at least with this info you can get the general idea. Lets start talking about some specifics!
Fluorescent
Normal Output (NO): These lights are the lowest on the totem pole. They are the standard lights that come with aquariums when you buy them. They are really inappropriate for most set ups as they are not powerful enought to sustain corals for long term periods. However, one potential application which may find NO lights appropriate is in a refugium. They can be bright enough to grow algae which is the purpose of a refugium. The only advantage of NO lights are that they are cheap, readily available in a variety of sizes, lengths, and kelvin ratings.
High Output (HO): These are the next step up from NO lights. These lights again are available in a variety of lengths, sizes, and kelvin ratings. These are capable of sustaining some corals for a long time and can be used in some reef aquariums. A relatively new light on the market are the new T5's which are HO lights and have so far established themselves as an acceptable light source. These bulbs require a special ballast to drive them.
Very High Output (VHO): Same as above only even more powerful. These lights are again capable of sustaining a variety of corals longterm. The bulbs are readily available in a number of sizes, kelvin, lengths, etc.
Power compacts (in my opinion) are probably somwhere between HO and VHO. I personally am not a fan of PC's because of their reputation of breaking easily and up until recently they did not have a true actinic bulb available in PC. However they do now apparently.
High Intensity Discharge (HID)
Metal Halide (MH): As of now, these are the cadillac of the lighting world. These are VERY bright lights which are capable of sustaining all types of coral. They come in numerous Kelvin ratings and wattages ranging from 70w up to 1000w. The most commonly used in reef aquariums are 150w, 175w, 250w, and 400w. There are two types of MH lighting, mogul base which are large bulbs that are encased in a Glass housing that screw in to a socket similar to a standard light bulb. Then there are the HQI bulbs which are also known as double ended (DE) halides. These bulbs do not have a glass housing and thus need to be shielded before being used. They snap into a special socket. The HQI bulbs are generally brighter. Using MH bulbs will give a nice shimmering effect in the water where as fluorescents will not . . . a nice benefit in my opinion!
MERCURY VAPOR - The Iwasaki DL Mercury Vapor bulb run on a Mercury Vapor Ballast is about the best bang for the buck out there in terms of PAR per penny. Some report that it grows very healthy corals very quickly but that most SPS grown under the Iwasaki are Brown and the light is fairly yellow.
Lights NOT acceptable for reef tanks:
Halogen
Incandescent
High pressure sodium
The reasons behind this are generally lack of PAR, wrong kelvin, or just plain impracticality.
So lets briefly return to that watts per gallon thing . . .
In addition to the notion that watts measure input, not output, another thing to consider is that as a tank gets deeper, the less light is penetrating the water. For example, if you have a 20 gallon tank that is 5 inches tall (its an example, not reality), and run 100 watts of NO fluorescent lights, thats about 5 watts per gallon. But what if the tank was still a 20 gallon tank and 100 inches tall . . . do you think that its going to be just as bright on the bottom as the 5" deep tank? I hope not . . .
Another thing to consdier is that MH light penetrates the water better than fluorescent light. So 400w of MH does not equal 400w of VHO. In sum . . . the watts per gallon rule is JUNK!
So how about corals? What lights do you need to keep what corals? This is something that is FAR beyond the scope of this thread. It would take a whole book to adequately cover this topic so I will just cover the bare bone basics . . . .
Soft corals (those without a calcerous skeleton) in general require the least amount of light. You can keep a soft coral tank with using all HO lighting.
Large Polyp Stony (LPS) corals require more light than soft corals. They can be kept under HO, but VHO would be better.
Small Polyp Stony (SPS) corals require VERY bright light that is only achieved with MH lights. SPS kept under less than MH will fail to thirive if they even survive. Clams also fall into this category.
I know that there is a LOT more that needs to be covered on this subject. Please feel free to ask questions, make corrections, ask clarification, etc . . .
Like I said, this is a highly debated subject, and I am no expert . . .
Enjoy!
