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A FAQ detailing the basics of what a reef tank is, including what you will need, what you need to consider, and when you need to consider various aspects of the hobby.

A. Tank Basics
B. Stand and Hood Selection
C. Lighting - The Great Debate
D. Sump
E. Filtration
F. Water Quality
G. Sandbed and Rock
H. Curing
K. Timing
I. Source of Livestock
J. Detritivores
L. Livestock selection
M. Maintenance

A word about setting up reef tanks

When you set up a reef tank, you are making a commitment to maintaining as close to an ideal environment as you can for the corals, fish, and other invertebrates you will be housing. You need to research everything before you begin, it will save you money, frustration, and animal lives. There are tons of resources available; from online libraries to books to online bulletin boards to chat groups. Read, read, then read again. There are many different opinions in this hobby, some wives tales, and a great deal of 'making it up'. We suggest you read everything available to you and form your own opinions. Investing in a few books will mean a great deal more satisfaction in the long run. From the moment you purchase your first animal for your aquarium, you are taking the responsibility on of maintaining a proper and healthy environment for it.

That said, it follows that you should not skimp on the proper equipment. In order of need (for quality and a proper environment) for a reef tank, you need the following items: good lighting, good skimmer, and good quality live rock. Do Not Skimp! You will regret it later. Thats not to say you cannot do it yourself (Ozreef has great listing of items: ), but please don't buy the cheapest, just because its cheaper. Buy quality. You won't regret it financially because in the long run you would likely have to buy the better item anyway and have wasted the initial purchase.

A. Tank Selection

There are a number of factors to consider when choosing an aquarium for your home, office, dorm room, or the like. Most of you will already have a tank by this point, but in order to help out those who may not have all the details there are benefits and downsides to many of the commonly available aquariums. The first consideration is location: Where will you put the tank? It is a good idea not to place a tank in a kitchen or a workshop or basement where chemicals are commonly used or frying pans spray vaporized grease into the air. Consider the health of the livestock. Also look at what traffic passes the area, where are the heating/cooling vents, and other such items that might be a concern. Measure available space and decide on an aquarium from that perspective. But, what about those people that aren't restricted to a given size? A general rule of thumb is to get the largest tank you possibly can. Why? Because (and trust us here) if you don't, you will be upgrading in the not too distant future. That's not the only reason though. Consider the issue of stability. A larger tank is more volume, which means more time for temperature, salinity, or pH swings as well as larger volume effects on diluting out problem compounds. An even more pertinent consideration is 'what will your tank house?' If you want to keep an eel or a shark, for example, you need to have the proper tank size to handle such an animal. Be cautious though, many floors won't support the weight of a full 400 gallon tank! Have a look at the following to give you an example of how most people set up modern reef tanks:

Acrylic vs Glass

Once the issue of size has been decided, the next issue that usually arises is the question of acrylic or glass? Each has benefits and each has weaknesses. You need to decide on your own, but here is a list of what each has as a benefit:




lighter per size



very clear

green when thick


very easy!

not very


custom are more common

standard sizes more common

nuisance growth

corraline grows fast, hard to remove

slow encrustation


seams are weakness, bow along long faces

seams are weakest

I have a preference for standard size glass tanks because I am clumsy and lazy, which means that I am more prone to scratch an acrylic tank. Although, having seen both, acrylic is a much clearer material that really helps you see details in the tank. I would suggest that you search around and be certain of what you want. A note for those purchasing used tanks: Look it over very, very carefully before purchasing. The larger the tank, the better a job of looking at the seams and structure as it's a huge investment and most insurance won't cover a living room flooded by a faulty tank.

Drilled vs Hang-On Overflow

Having been on both sides of this issue, I am a huge proponent of having a tank drilled to accommodate a sump underneath. Its certainly not mandatory, but it will prevent accidental overflow if a siphon on the overflow breaks during a power outage. There are many methods to making overflow boxes and standpipes. There are a variety of commercial types you can purchase or DIY versions you can make at home. The only features that are mandatory are that they skim the surface of the water, they can handle the flow you are putting through them (1" ~ 900gph; 1.5" ~ 1800gph), and they have protection against snails and debris plugging the intakes.

Braces and Light Dispersion

One last consideration that you should be aware of is the presence of braces in the top of most tanks. Some are cheap plastic, some are glass, other tanks have none. If your tank has braces, you will have to adapt your lighting to account for them. Placing a metal halide lamp too close to a plastic brace can be a disaster. Each bulb will need to be centered between the braces for maximum light spread inside of the tank. Placing a strong bulb near a brace will also cause heavy shadows inside of the tank.

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B. Stand and Hood Issues


Depending on the setup you wish to employ, most people will be placing a great deal of equipment underneath a tank inside of a stand. You want to optimize this open space to accept all the new toys you will need to keep a successful reef. Some of the items usually placed under the stand are: a sump, pumps, heaters, calcium or nilsen reactors, refugiums, test kits, and any other item you use commonly with fish tanks. See the diagram listed in the beginning for explanation. Stands should be well sealed against leakage as everyone spills saltwater on the stands and over time, this could lead to peeling of plywood layers or even splitting of solid wood.

Hoods - Retrofitting

Considering the hood style or needs, you need to go back to that primary question again: What animals do I wish to maintain? If you will need metal halide of a stack of VHO lamps, then you need to account for those in the design of a hood. See the lighting section.

Retrofitting means that you take an existing hood (canopy) and alter it to accept the lighting you wish to install. Many hoods that come with tanks are designed for fluorescent lighting, which means that they are too shallow or not enough ventilation to accept metal halides. These will need to be altered to function well and safely. Retrofit kits are available through most stores and vendors ( to outfit existing hoods to make them reef friendly.

Retrofitting is not necessary. Many manufacturers make both standard and custom hoods for reef tank setups. Some are even designed to be inserted into existing hoods.

Ventillation is a key issue. Modern lighting is hot (whether PC, VHO, or MH) and air needs to be vacated from the hood in order to prevent too much tank heating and/or destruction of the hood and tank braces. Increasing ventilation also increases evaporation which will cool the tank of excess heat and allow topoff of kalkwasser.

The last consideration in a hood is light spread. Orientation of lights, length of fluorescent tubes, and the number of lights needed to cover a given area all have a role in the design of the hood. Reflectors need to be incorporated to prevent wasted light as well. They reflect light that is given off away from the tank back towards the tank and its occupants.

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C. Lighting - The Great Debate


Metal Halide (MH) - This is the be all, end all of reef lighting. In most cases, any coral reef animal can be kept under this lighting successfully and with the best coloration. Wattage ranges and typically can be found in 70, 150, 175, 250, 400, and 1000 watt bulbs. Bulbs vary in color temps (K for Kelvin, the higher, the more blue it appears) and have differing effects on coral coloration. Ballasts can be electronic or tar style (cap and coil).

Very High Output (VHO) - This is what the hobby was built upon in the last 7 or so years. The high output bulbs allow for keeping some sps corals and all soft or lps corals successfully. With enough VHO, almost any coral can be maintained.

Power Compact (PC) - These are also a fluorescent light. Comparable to VHO in output, although not shaped like traditional tubes, these bulbs are shorter and don't span the tank as well, but work great for smaller tanks.

Normal Output (NO) - This is the standard fluorescent lighting that you have in home or office or over houseplants. Generally not advisable, although acceptable for some specific animals.

The debate surrounding 'necessary' lighting is a strong one. I won't attempt to promote one type of lighting too heavily over another as no one is settled on the issue yet. One common misconception, however, that I will address is "wattage per gallon". It's a useless number, especially in consideration of all the various animals that we try to keep in our aquaria. A better method is to again ask that question, "What animals do I wish to keep in my tank?" and use that as a starting point for answering the lighting debate. Clams (most anyway) should not be kept under too little light as they will turn brown and deteriorate over time. There is a true difference between "required or satisfactory" and "ideal" lighting. Would you like to live in a 4x4 cell with a single 5W bulb? As a general rule (and this is by no means set in stone):

Clams, colorful sps and most anemones: MH lighting
Tan/brown sps and lps: VHO/PC lighting in high quantity
Some lps and soft corals: VHO/PC/heavy NO

If you do a cost analysis, based on the longevity of bulbs, you will find that over the long term, MH lighting is cheaper as far as replacement costs. One measurement that might work well if you want a number to go by is to figure out watts per surface area. This gives a better number, but the effectiveness varies by light type. Remember, the deeper the tank is (top to bottom) the more light you need as its lost in water.

The final concern that some people have is a combination of increased heating of the tank due to intense lighting and increased power consumption. Both are real and both occur, although each can be dealt with by strong ventilation or other mechanisms.

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D. The Sump


A sump is a box that holds all the gadgets that clutter the main display tank. It allows for easier dosing of chemicals, cleaning of skimmers and, generally helps with organization and oxygenating the reef. The process is relatively simple. Water falling from the tank above (via drilled bulkheads/hang on overflow) falls into the sump, where it is heated or chilled or skimmed, etc. and then is pumped back to the main tank. Some people use a portion of the sump as a refugium (or a lighted algal scrubber), some people use it as a cryptic filter (sponges and other filter feeding organisms colonize it to help filter the water), and some use it as a place to dose additives. In general, it helps oxygenate the water and gives users a place to increase evaporative cooling by placing fans nearby. It also allows for increased circulation in the tank due to returning water velocity. An added bonus to using a sump is that it increases tank volume which is beneficial (see tank sizing above).

In regards to a sump, you must consider the fact that when the power goes out on your tank, water will back siphon into the sump, down to the level of the return opening. In order to prevent much backflow, holes need to be drilled at or just slightly below water line on the return end (termed siphon breaks). But, the sump must have enough residual volume to accept the backflow of water without spilling over. That means that the sump should be run less than full during normal operation. The size of the sump is typically determined by available space, but more volume is always better as it allows for more buffering as mentioned above.

Another great use for a sump is topping off the tank. Whether its automated or manual on a daily basis, topoff is fresh water. Therefore you need to allow it space to combine with existing tank water. A sump allows for a high degree of mixing and for the time needed before it rushes back into the main tank.

Heaters should be sufficient to heat the entire volume of the system. A typical setup uses two heaters in order to prevent problems arising due to a failure (and resulting cold water) of a single heater. A typical 55g aquarium can be heated by a single 150W heater assuming ambient room temperature is kept moderate.

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F. Filtration

Skimming, skimming, skimming. Successful tanks can be kept without the use of a protein skimmer (foam fractionator), although for the beginning aquarist I highly advise the use of a good quality skimmer. Skimmers work by forcing air and water to mix causing the organics in the water to stick together. This creates foam which is then pushed out of the skimmer and removed from the system.

Other forms of filtration do work as well. Hang on filters work fine for small tanks if water changes are done on a regular basis. The use of activated carbon is highly suggested as well as it works to remove organics much like a skimmer.

Undergravel and canister filters are not suggested for use. They are a risk to the animals in the tanks due to the fact that anaerobic pockets can develop and release highly acidified water to the system (not to mention stink A LOT!). This is especially an issue when the power goes out for a couple of hours. They also reduce the efficiency of the sandbed to reduce nitrate to nitrogen gas to be released into the atmosphere. Biomedia (bioballs, filter floss, etc) is also generally not used any more. These will cause a great deal of aerobic degredation of ammonia to nitrate, but the nitrate is the end product which causes it to build up in the system to levels that can cause stress to corals.

A good deep sand bed combined with a good quantity of live rock and good circulation provides a great deal of filtration, especially in combination with a good skimmer.

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F. Water Quality

Water Source

Every water supplier, whether a city of a county or a state, must present to anyone who asks a water quality assessment. These are done on a regular basis to keep up with EPA regulations concerning the levels of various things in drinking water. I highly suggest that anyone who is interested in reefkeeping request this document from your water supplier. It will note important items such as pesticides, copper, ammonia, and many others. You might be surprised at what you are consuming. Water quality varies greatly from region to region, aquifer to mountain lake, to river water sources. Because of this fact, its impossible to make a recommendation about an individual's water. However, in order to promote a healthy reef, most hobbyists need to have RO/DI water for use in their tanks.


What is RO/DI? It stands for reverse osmosis/deionization. That means that water is forced thru a membrane (that leaves many molecules behind) via pressure (the RO portion) and then run across a column of mixed resins that grab anything that has a positive or negative charge on it. The water coming out of the other end is usually very pure. Most RO/DI systems that you can purchase for your home also have size exclusion filters and carbon filters in line before the RO membrane. Starting with pure water in making salt mixes (or using it as topoff water) means that you will have a consistent water quality going into your tank. Be sure to purchase an RO/DI setup that can produce enough water in a time of need to keep a tank going or keep a 30 gallon bucket of RO water for emergencies.

There are other methods of purifying water, though most are not nearly as thorough as RO/DI. Distillation is heating water so that it evaporates and then cools and collects. This removes most salts but not volatile compounds. Spring water is not necessarily filtered at all and should be avoided.

One other issue to be aware of is that if purchasing your water from a local fish store (LFS) or a grocery store, they may not be keeping up with replacing filters and membranes. This could lead to poorer water quality and algae issues in your tank.

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G. Sandbed and Live Rock

Dr. Ron Shimek proposed a while back that deep sand beds had numerous properties which will increase the health of our captive reef systems. The increase in critter diversity is one of its strongest attributes. The other is that when deep enough with a fine enough grain size, micro-aerophilic zones (very very low oxygen, nearing anaerobic) are attained. In these zones, bacteria convert nitrate to gaseous nitrogen, which then is free to leave our tanks. The same process occurs on the inside of the rock we use in our tanks as well, once colonized by the proper bacteria (the so called 'cycling' of a tank is solely to allow these bacteria to colonize and shift numbers).

The sand grain that seems to be the best is oolitic grade. Aragonite is best, although silica sand also works. A mix in grain sizes appears to be a true benefit to the critters that live in the sand as well. "Live sand" as sold, is basically just sand that has bacterial and critter life already in it, and so prevents any cycling from occurring.

Live rock follows the same definition, its rock that has the bacteria and other macro life already on it. But remember that if its ever removed from the water for any length of time, some die off will occur and possibly cause another small cycle (even if not visible in your volume of water).

Typical sand beds are 3-6 inches in depth. Typical rock loads are from 0.5-2 lbs per gallon, depending on personal preference.

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H. Curing or Cycling

What is a cycle? Do I have to force a cycle?

A cycle is a process whereby bacteria are shifting their populations in both total numbers and in population types to deal with new food sources. When a tank is new and live rock has just been added, the die-off from the rock breaks down and releases ammonia. That ammonia is taken up by one type of bacteria and given off as nitrite. The nitrite goes through the same process and then is released as nitrate. Those processes happen in the presence of oxygen. Deep in the sand and rock, another type of bacteria exist in low oxygen areas that convert the nitrate to nitrogen. Nitrogen is completely non-toxic and can leave the system as a gas. That is the way in which our tanks cycle. If you start a tank with cured live rock (if truly cured and lacks large clumps of plant or sponge or the like material), then no cycle may be witnessed. If livestock is added slowly, the bacterial populations increase on demand without stressing the system.

Ammonia and nitrite are highly toxic compound generated from decaying matter and from fish waste. If a tank has any detectable ammonia or nitrite, you should not have any living animals present. Ammonia is more toxic in saltwater than in freshwater due to the higher pH of saltwater.

Our recommendation in this day and age is to NOT use livestock of any form to induce a cycle in a tank. Use live rock, cured or uncured, it matters not. Do NOT use dead animals either, it's the same reason. They are both methods from the past that have no place in today's reefing world. Forcing a cycle is not a real benefit if you stock slowly and properly and monitor a young reef tank. Many even believe that no swimming animals should be added until after a few months have passed. More on that later. The reason that you need no more than live rock is twofold: first, the rock already has a full complement of the bacteria you will need to get the tank going and secondly, there is enough 'matter' on the rock to provide 'food' for the bacteria that are the reason your tank is cycling.

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I. Timing

An initial cycle can last anywhere from zero days to 8 weeks. This depends on many factors, including current in the tank, filtration (skimming), amount of die-off from live rock, temperature, etc. A cycle can be followed by testing ammonia, nitrite, and nitrate. A cycle is fully complete when ALL of the above read 0.

Livestock should be added very slowly. Make decisions based on requirements for each individual animal. Start with snails and detrivores (the so called 'clean up packages are fine) when the cycle is completely finished and there is food for the snails. Most places sell more animals than needed and some of them die out from lack of food, so be careful how many you add at once. You can (and will have to) always add more at a later time. Adding fish depends on the fish's behavior. Those fish with tendances to consume the small critters in the tank should be added at a much later time to allow the detrivores and other critters to populate the tank. Many people say no earlier than 6 months. For algae eating fish, such as tangs, I would suggest 1-2 months post-cycle before adding them. They tend to graze algae, but not process it well, so that adding them to a new tank can extend or restart cycles.

Above all, add the livestock slowly and with ultimate regard for its needs. Don't purchase a vlamingi tang to place into a 55g aquarium, for example.

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J. Livestock

Sources and Methods of Collection

We would like to take a second to make you aware of various collection techniques and to propose to you to only buy captive raised livestock where possible. Most of you have heard about cyanide fishing. The details are as follows: 1) a fishermen wants more income so he collects more fish 2)fish are not easy to collect by hand so they employ the use of sodium cyanide as a liquid in a squirt bottle 3)chasing little fish into coral heads (which is the natural place for them to hide), the fishermen gives the bottle a squeeze while aiming into the coral head and the fish are stunned (or killed) 4)because the fish move very little while stunned they take out their crowbars, break the coral head into smithereens, and then net the stunned fish. Not only does this cause the physical destruction of coral, but the cyanide while only stunning fish kills the corals. Areas downcurrent of the use show devastation after a short amount of time. It is for this reason that fish from any old source should not be selected when alternatives are available. Buy only net caught or captive raised fish, thereby pushing the demand for fish and corals in the proper direction. You as a consumer make ALL of the proper changes.

These destructive fishing practices, as they are called, are numerous and all have lasting effects, not only on the reef but on human health and ecosystem health as well. Groups exist that push change, but it is slow in going and because of that, the consumers have the majority of power to institute change. Please make fish selections wisely and ask your local stores to carry livestock that is not as destructive to everyone involved.

In order to select healthy livestock, you should see the fish in a tank in the LFS. You can watch its behavior and interaction with other fish to determine its fitness. Ask to see the fish eat (and try to get the employees not to spook the fish in the process). Fish that will not eat or that have pinched in stomach areas should not be purchased. NEVER buy a fish out of pity. This only promotes the cycle of bringing in low quality or illegally captured fish. Along with eating behavior, make sure the fish is not 'scratching or flashing' items in the holding tank and that it is not showing labored breathing.

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K. Detritivores

Detritivore is a fancy word for an organism that eats detritus or debris. There are many different types available, so I will only say a few words about them.

Bristle worms- Great detritivores. Only a few species out of hundreds are dangerous to our tanks and those very rarely ever show up. They are the fire worms and they tend to munch on soft coral.

Hermit crabs- Moderate detritivores, better omnivores. They'll do damage to your snail populations, but are still alright to have in your tanks. Look out for large ones and make certain to feed them and provide them with larger and larger shells. Scarlet hermits are the least destructive in comparison to left-handed, blue leg, and red leg hermits.

Snails- These come in all types and sizes. Nassarius snails take the place of hermit crabs and eat detritus. Most of the rest eat algae.

Brittle and Serpent Stars- Serpent stars are purported to be dangerous around small fish. These stars hide in rock piles and stick their feet out to catch passing food. Ok detritivores, better for the cool factor. There is a small version of the brittle stars that many people have quantities of that also make great detritivores, commonly referred to as 'mini-brittles'.

Sand Sifting Stars- These cruise around in the top layer of sand eating bacteria, detritus, and little critters that happen to get in the way (or not out of the way). Used by some people. Avoided by others.

Others- There are tons of other types of detritivores. Many are sold as 'kits' from retailers. These include amphipods, copepods, mysid shrimp, bristleworms, and numerous other things that run around beyond the limit of our vision. Great to have as they feed fish and corals and keep a tank clean. Some 'clean up' packages that are sold have items in them that you want to avoid for the general wellbeing of your reef tank. Examples include: horshoe crabs, sand sifting stars, large serpent stars, flame scallops, and arrow crabs.

Detrivores can be added to a tank after any cycling is complete (complete meaning 0 ammonia, 0 nitrite, and preferably 0 nitrate). They'll spread out and colonize the tank and keep diversity levels up. Just make certain that you feed the critters so they don't begin to consume each other or die off.

Please see the hitchhiker FAQ for pictures and details:

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L. Livestock Selection

Every animal comes from a specific region in the world. Their requirements for everything differ and as an educated hobbyist, you should strive to never purchase anything you haven't researched. The website is a great reference. For each animal, you should know the following: depth collected from (lighting and temperature affectors), normal water flow conditions, dietary requirements, aggressive tendancies, communal nature or not, ability to survive in captivity, maximum size, and growth rate. These data will help you greatly in establishing a peaceful and stress free tank for your future pets.

You should also research the location and biotope/niche your potential purchase is from... an example is catalina gobies. They are a temperate, cooler water fish that does not survive well in our warm water tropical pacific tanks. Please try to find fish that will survive with the tanks parameters.

Some other considerations for livestock are common sense items such as the placement of powerheads relative to corals or within range of the bottom (so as not to suck up snails or cucumbers). Don't purchase venomous or poisonous fish and invertebrates if you don't understand how those toxins work and what risk they pose. The list goes on and on… please think before you buy.

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M. Maintenance

Willingness to devote time to various maintenance aspects varies greatly by person and by setup. Some systems are totally automated. But, in getting into the hobby of reefkeeping, you need to take the time to keep your equipment in good working order. For some people, this starts with regular documentation or record-keeping. Its wonderful if you can manage it as it will tell you what you did and when to backtrack when problems arise.

Testing the aquarium water quality is a good idea to keep water parameters in-line. Typically, testing for calcium, alkalinity, pH, and nitrates is sufficient. There are many other test kits and each can be used if needed, but in maintenance of the tank, the above are typically the only required. A pH probe is a common and relatively inexpensive monitor you can purchase now that takes the place of regular pH titrations. The following shows typical ranges for each parameter in a reek tank:




8.0 - 8.3






0 - 30 (lower is better)


400 - 500 ppm


10 - 14 dKh

Pumps and skimmers especially need to be cleaned on a regular basis. Some organisms really like high flow, low predation environments and will colonize the inside of plumbing or pumps or skimmers. Periodically, usually in month blocks for skimmers and every few months for pumps, these items need to be taken offline and soaked in an acid solution such as vinegar (don't use soap as it will cling to the surfaces and won't really clean anything). It will dissolve any calcium deposits and skeletons allowing more water to flow through and it will keep pumps alive longer by removing grit. Skimmers need to be tweaked and cleaned to remain in good operating condition depending on the bioload of the tank and the type of skimmer. Be warned that a skimmer may take a little while to 'break in' again after a cleaning. This usually isn't long.

Lighting should be cleaned periodically as well. Evaporating and splashing water tends to cause light fixtures and bulbs to become coated in fine salt. Use a wet rag (with the power off and the bulbs cool!!!) to wipe them down and restore their natural luster. Placing a wet rag on a hot bulb is asking for glass shards.

Don't use magnets for acrylic scraping as they tend to be dangerous. If a single grain of sand or calcium shell is picked up it will scratch. For glass, an occasional razorblade is perfectly acceptable so long as its edge is clean and free of rust.

Topoff should be done as often as possible if you don't have an automated system. This prevents strong changes in salinity and keeps skimmer and sump water levels steady.

This FAQ produced by wade for (c) 2002

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Created by liquid
Last modified 2006-11-23 04:56