Watching a marine aquarium is a great pleasure and probably one of the major reasons why so many keep them. With a reef system sometimes a new arrival is seen to appear, or a species of coral that is already present appears somewhere else.

On a few occasions I’ve noticed arrivals that must have come in with coral rock, such as a very dark and tiny crab that was very timid and only appeared at ‘dusk’. Its presence was shown by an exploratory claw appearing out of a crevice. The crab hasn’t been seen for a long time and no doubt has gone.

Corals too can appear when new live or coral rock is introduced. In this case the coral type is already present in the aquarium with a fairly large colony, and the new appearance is in a completely separate part of the aquarium.

As far as I can tell, the main colony is a Rhodactis species (the purchase was made years ago and the dealer didn’t have a clue). Rhodactis are also commonly known as hairy mushrooms and mushroom anemones. I think it could possibly be Rhodactis indosinensis – but is this correct as most grow larger than my specimens? Maybe they are Discosoma species. The colony is receiving plenty of light as it is half way up the reef (about half way up the aquarium depth). The new one, however, is not; it is right down at the bottom. The aquarium is 24″ deep (21.5″ from lights to coral). Further, this new growth is at the end of the aquarium and is partly shadowed by another coral.

Is my lighting system powerful? No is the answer, it’s a fluorescent array of five tubes, three marine whites and two marine blues (actinic). They’re not even T5’s, they’re T8’s. The reef is furnished with soft corals and they are perfectly happy but I had to wonder at the growth of this new one. The blues will penetrate well but even so….

The original colony is in an ideal spot apart from seawater flow which is a bit too vigorous, they prefer weak flow. However, I’ve left things as they are as the mushrooms are clearly healthy and open well, though not to as large an extent as with lower seawater flow.

The new one is the reverse; it’s in an area of slow flow. However, as said, I wondered about the light. It has been slowly growing for about 8 months now and has reached a size of 3″ across, which, because of the slow seawater flow, is full expansion. However, though I believed the slow growth must be because of light, or at least the lack of it, it seems this could be wrong. Looking at one of the references available to me * it seems that though light is no doubt an influencing factor it isn’t that important, as strong lighting is not required by Rhodactis species though they will tolerate it. Discosoma species prefer in many cases reduced light.

How did the new growth appear? It is possible it’s by natural detachment, but in this case is more likely to be my error. From time to time I have to get out the trusty and sharp scissors and reduce the colony to prevent interference with other species. Part of this is catching the detached parts. These corals are easy to ‘frag’ so if a small part escaped my attention and lodged it is more than likely to grow.

So there we are – what started as a general belief followed up by some simple research has turned my notion upside down. Goes to show how important basic research is. As far as identifying the species, I’d need a marine biologist and I bet there’d be uncertainty even then.

(*Reference: Aquarium Corals. Eric H. Borneman)

What is the most important part of a marine system? Lighting? Well no, it isn’t, seawater quality is the number one with both fish only and reef aquariums.

High seawater quality means there shouldn’t be any indication of ammonia or nitrite. Nitrate should be as low as possible (the guideline for a reef system is less than 10 ppm (parts per million) and for a fish only less than 30 ppm. Phosphate should preferably be undetectable. pH should be stable in the region 8.1 to 8.4. SG (specific gravity) for a fish only should be stable within the range 1.022 to 1.025, and in a reef system 1.024 to 1.025 (there are variations with SG which more advanced aquarists use for specific purposes). With a reef system there are more seawater parameters that could be monitored but those given are the basic ones.

So what has seawater quality got to do with lighting, this text is about lighting according to the title.

There are occasions when an aquarist is completely at a loss to explain why the corals are not as they were, with reduced growth and less expansion. Tests have been carried out on the seawater and it is top notch. What could be the problem? Perhaps a disease that is hard to spot? In fact it could be the lighting. Great care is taken when setting up a reef system to ensure the lighting is suitable and the corals, hard or soft, will confirm this.

With a fish only aquarium the lighting is not of such great importance. Its function is to permit the fish to see and the aquarist to see the fish. In addition, if the lighting, which is usually fluorescent tubes, is chosen with care the fish colours can be enhanced. Some colours react really well to ‘marine white’ tubes, and likewise to blue (actinic) ones. There isn’t any reason why more than two tubes cannot be used, but at least two should be in use, say one ‘marine white’ and one blue (actinic). Doing this not only assists with fish colouration, it permits the aquarist to create a ‘dawn/dusk’ sequence. Using electric timers, the blue tube comes on first, then half an hour later the white. At the end of the day the white goes off followed by the blue. This avoids washing the aquarium with sudden light and plunging it into instant darkness, both bad practices.

The reef aquarium is a different story. With these systems lighting is a close second to seawater quality. Most of the corals commonly kept have zooxanthellae in their flesh. Zooxanthellae are single celled algae and the coral gets its colour from them. In addition the corals obtain food as ‘rent’ from the algae; authorities have quoted the level of food supply as 80% or more. Algae, as other plants, require light in order to photosynthesize. The light needs to have sufficient power to penetrate the seawater to the depth of the corals and reach the algae. Power is measured in watts (W). If power is insufficient then the algae will get too little, this is why different power requirements are quoted for aquariums with different depths. In addition, the spectrum needs to be suitable. Light is measured in Kelvin, otherwise known as the colour temperature. Though there is more than one colour suitable for photosynthesis with some corals, blue is the one commonly used by aquarists. Blue penetrates deeply into the seas and oceans. Generally all light types use the Kelvin scale. If metal halide lighting is in use, the bulb(s) commonly used are 10000K and 14000K. The higher the number, the more cold or blue the light appears. Many aquarists use blue (actinic) fluorescent tubes alongside their metal halides. Many commercially produced metal halide arrays incorporate these tubes.

With reef lighting it is also advantageous to have a ‘dawn/dusk’ sequence. Whether the main white lights are fluorescent or metal halide, having blue tubes allows the sequence to be arranged.

So corals, or rather the zooxanthellae in their flesh, need lights that have a suitable colour and in addition the lights need to have enough power to penetrate the seawater.

Provided the aquarist has chosen the correct lighting system in the first place and other requirements are as they should be, the reef display should be lovely. This continues for longer than a year or more when eventually the aquarist notes that the corals aren’t as they were, as said earlier. There appears to be a slow reduction in extension. Perhaps there is a slight and maybe continuing change in colour. Again as said, the aquarist gets out his/her array of test kits but nothing appears wrong, the seawater is still of high quality. How about the lights?

With a fish only system there doesn’t need to be too much concern about the lights. As said they are normally fluorescent tubes and need changing when there is clear discolouration or blackening at the end of the tubes. It is not long after this point has been reached that the tubes are likely to start flickering or fail.

With a reef system the lighting needs more careful monitoring. To the aquarist’s eye there seems to have been no change to the light, as the tubes and/or bulbs switch on normally and they seem just as bright. This is not so however. As time passes the tubes and/or bulbs start to reduce in power which means that, given time, less light will reach the zooxanthellae. In addition, over time the spectrum shifts slowly and the painstakingly chosen lights emit a changed colour, again something the corals will not appreciate.

The best way that a reef aquarist can proceed is to keep a notebook; it only needs to be a small one. In it can go all sorts of memory joggers – including when the lights were first turned on. The manufacturers usually suggest in their documentation how long the lights should maintain their original specifications. There is considerable discussion within the hobby about light reduction/change periods, some suggesting that lights should be changed every three months. I have no facts or scientific reports to argue with, but I feel that period is definitely safe but rather short. Changing the lights no later than one year seems to be a reasonable general guideline. My reef is lit by a fluorescent array, and I change every nine months and have not had any problems.

The aquarist carries out many maintenance activities, a number of which are quite rightly concerned with seawater. There are the test kits that need to come out of the cupboard regularly, the routine seawater changes that partially replace lost trace elements and dilute the sometimes troublesome nitrate. Then there’s cleaning that very useful device the protein skimmer and ensuring that seawater flow is optimal. Plus the rest.

The lights are just there. They may get an occasional wipe with a damp rag but that’s usually all. They’re very dependable and all that is needed is a bulb/tube change after a specific time lapse. This will keep the corals happy if other parameters are good.

Happy corals mean a happy aquarist.

There’s a form of lighting that presents not a single headache and that is moonlight.

In the wild as everywhere else there is day and night, plus the transitional periods dawn and dusk. At night there is often moonlight which is missing from most aquariums.

Having moonlight is not essential. Corals are not going to suffer from the lack of it. Having mentioned corals and moonlight, isn’t it fascinating the mass spawning of corals on a reef, all of them triggered more or less at once.

Moonlight is optional. For those well-heeled aquarists with LED (light emitting diode) arrays it is possible that it is built in and ‘on’ times can be programmed. For most of us it is an extra purchase.

When all the lighting is off except for moonlights the effect on the captive reef is lovely. Weak shafts of light descend onto the corals, flickering across them. It can make the night period quite beautiful and draw the aquarist to have a look at a time when usually he/she wouldn’t.

Moonlights are a small array of blue LED lights. Usually they are supplied in a small unit, with perhaps five or less LED’s. There are larger units. Sometimes they are powered by a plug-in transformer style electricity supply. Their demand for electricity is very low, so very little will be added to the electricity bill.

As said, putting moonlights onto an aquarium is optional as there isn’t a technical requirement. Very advanced aquarists could well experiment with them to see if corals could be induced to spawn though this would be difficult and time consuming. Most of us would use them purely for the lovely effect, and expand the period when the aquarium acts like a magnet.

Even though metal halide is so good at lighting reefs there are disadvantages. There are two major ones, the first being that metal halides are electricity hungry and will add significantly to the aquarium energy cost. The second is that they generate a lot of heat. It is this second disadvantage that is being considered.

The lighting has to be hung well above the seawater level and this is because should the protective glass or bulb be splashed it could crack as it is so hot. It needs to be remembered that if the glass is to be wiped over with a damp cloth it needs to cool down first.

We nearly all like sitting in a favourite spot in the sun, feeling the warmth. Metal halides bulbs are a little like the sun in that they radiate considerable heat and unfortunately this could cause trouble. Many reef keepers use cooling apparatus to keep the temperature of the seawater under control though this for most is only in summer. This apparatus could be fans in the lighting hood, a pedestal fan alongside the aquarium, a ‘chiller’ (electric seawater cooler), or perhaps a combination. Stability of seawater parameters is important and this includes temperature. If the temperature climbs too high livestock welfare is in jeopardy. If the temperature is noted to be climbing much too high then the first action is to turn off the metal halides until cooling equipment can be used. The aquarium shouldn’t be plunged suddenly into total gloom, so the blue (actinic) fluorescents can be left on.

There is another danger from metal halide heat as well, and I wasn’t aware of this until recently. There are aquarists who use acrylic aquariums and these aquariums, like glass ones, have stress bars built in across the top. It is reported that the major failure with acrylic aquariums is where a metal halide bulb is directly above a stress bar. The heat softens the acrylic which then stretches under the outward pressure of the seawater and splits or worse could occur.

So if it is possible to move the bulb away from the stress bar this should be done. If the metal halide is then off centre this could be all right, check the light coverage. The guideline is that a metal halide bulb at the correct height above the aquarium should light three feet of aquarium length.

One of these decisions is what type of lighting you should use above your aquarium.

It is my opinion that realistically there are two options available to guide you towards your decision:

1. Choose lighting which is appropriate for the animals which you hope to keep
2. Choose animals which are suitable for the lighting you have made the decision to purchase

Some people think that this is a strange way to decide however to me it makes perfect sense (but then in my head various things make perfect sense!)

Basically you can go out and purchase some lighting which is relevant to your budget and then design the remainder of your aquarium and livestock purchases around this lighting or you can design your aquarium system including the lighting around the livestock you want to keep.

For example if you have purchased a second hand aquarium system and this aquarium comes with T5/T8 fluorescent lighting and is 18 inches deep from top to bottom then realistically you are looking at either a fish only aquarium or a reef tank with soft corals and perhaps some long polyp stony (LPS) corals.

Another example following this trend would be purchasing a complete aquarium kit from your local fish shop where the lighting is included. In this example metal halide lighting is provided and the aquarium is 24 inches deep from top to bottom. In this example you could again keep a fish only aquarium or a reef tank with either soft corals, long polyp stony (LPS) corals, short polyp stony (SPS) corals or a mixture.

In the second example above if the decision was made to keep a fish only aquarium then the lighting will be overkill as a fish only aquarium does not need intense lighting for the welfare of the aquarium inhabitants. On the same scale if SPS corals were decided upon then other items will also be required to ensure that the aquarium is suitable. Strong water circulation springs to mind.

If lighting is being chosen based upon the aquarium inhabitants which in my opinion is a better way then the following can be used as a guideline:

• Fish Only – T8 Fluorescent Lighting
• Soft Corals – T5/Power Compact Lighting
• Hard Corals – Metal Halide/ LED Lighting

The above is definitely not set in stone as there are other variables which need to be taken into consideration the most important of which is the depth of the aquarium from top to bottom however this is normally only the case when corals are being kept.

If a fish only aquarium is your aquarium of choice then effectively all you need to do is provide lighting so that the fish can see and a dusk/dawn cycle can be created. This allows for the fish to be confident in its home as well as allowing you to see it.

When corals are being kept they require, dependent upon the species of coral strong lighting. Coral use the lighting as an energy source which allows the coral to thrive and grow as long as its other requirements are met for example calcium and water movement to name just a couple.

If you have an aquarium which is 30 inches deep then you will require stronger lighting than if you had an aquarium which is 18 inches deep.

The reason for this is the actual power of the lighting. Lighting power is measured in wattage – the higher the wattage the stronger the lighting will be.

If you had an aquarium which was 18 inches deep then quite probably a 150 watt metal halide would suffice to provide adequate lighting for hard corals to be maintained.

On the other hand if you had an aquarium which was 30 inches deep then a 250 watt unit or perhaps even a 400 watt unit would suffice to provide adequate lighting for hard corals to be maintained.

Wattage power in lighting is important as we want to ensure that the light unit has enough power to punch the light right to the bottom of the aquarium without losing colour. The deeper the light has to penetrate into water the quicker the colour from the spectrum is lost.

It is feasible that hard corals could be maintained in an aquarium that was 30 inches deep with a 150 watt metal halide unit however the corals would have to be placed in the top third of the aquarium.

Aquarium lighting is quite a complex subject especially when it comes to discussing the colour spectrum therefore I am not going to go into this in this post. Effectively at this point you want to try and push as much of the light right to the bottom of the aquarium.

One thing you do not want to do is allow light to not go into the aquarium. By this I mean allowing the light to go over the top of the aquarium into the surrounding room or allow it to be ineffective light due to a badly designed reflector.

Reflectors are used to direct as much light as possible from the bulb down into the aquarium. There are some designs which due to their design reflect a lot of the light back into the bulb itself rather than down into the aquarium which therefore means wasted light. A good reflector will reflect light around the bulb and down into the aquarium. The majority of good quality aquarium lighting units nowadays come with good quality reflectors but it is something you should be aware of.

Before looking at LED’s (light emitting diodes) it’s necessary to see what the LED’s need to be able to do to compete with metal halides.

Metal halide lighting systems are used exclusively for reef aquariums (if used on a fish only system then electricity is being wasted). Sometimes the aquarist is able to use fluorescent T5 tubes, but this depends on the depth of the aquarium – can the light penetrate deep enough?

In this case it is assumed that metal halide bulb(s) are needed.

Metal halide is basically a bulb that uses a filament, the bulb being inside a reflector. The bulbs are rated in watts and there is a range available, the most usual ones being from 150W up to 400W. The wattage is chosen according to the depth of the aquarium. The more watts, the more expensive it will be to run because of electricity usage.

The length of aquarium that a single bulb can light with usual width aquariums is 3ft (circa 91.5cm). This is a guideline not a rule. For a 6ft aquarium two bulbs would therefore be required, doubling the running cost.

The bulbs also need to meet another demand of the corals in addition to intensity and that is spectrum. A lot of the commonly kept corals contain zooxanthellae within the flesh. Zooxanthellae are single celled algae that are essential to the well being of the coral. In order to function (photosynthesize) they need light of the correct wavelength and fortunately metal halide bulbs can achieve this light output. In fact, there is a choice of outputs within limits.

Metal halide bulbs need to be changed regularly according to the manufacturer’s recommendations or the intensity could diminish and/or the spectrum shift.

To make the reef more natural (a goal which is being achieved more and more), many if not most aquarists incorporate one or two additional fluorescent tubes which are usually in the blue spectrum. This assists the delivery of the correct light to the corals and additionally, with the use of electric timers, gives a ‘dawn and dusk’ effect. That is, the blue fluorescent tubes switch on around half an hour before the metal halide, and switch off around half an hour after the metal halide. This avoids sudden bright light or sudden darkness, both of which are undesirable.

Are there any downsides to metal halides? Yes, there are two. The first one is running cost because the bulbs are electricity hungry. Consider a bank of two 400W bulbs ‘that’s not far away from a kilowatt per hour. If the lights are on between 8 and 11 hours a day’..well, you get the idea.

The second downside concerns the aquarium livestock. Stability in any marine system is very important and should be maintained as far as possible. Metal halide bulbs run very hot, and radiate directly into the aquarium as obviously they must. This heats the seawater and it is possible for the seawater temperature to rise unacceptably. If this is the case then the aquarist needs to purchase a chiller (seawater cooler) which is not particularly cheap to purchase or cheap to run. It may be possible for the aquarist to run surface air fans for cooling and many aquarists do this. In this case ideally the seawater temperature and/or time need to be linked into the fan system or, if the seawater cools down because the metal halide has turned off, it may be overcooled and the heaters will switch on for longer periods using more electricity.

So then, what about LED’s? These type lights are used widely nowadays for decorative and commercial purposes as well as more recently being of use to marine aquarists. Aquarists could already be making use of low-powered LED lighting in the form of blue lights that switch on after all the other lights have switched off. They simulate moonlight and give a really good effect, beams of flickering weak light in the seawater. These are not a competitor to metal halides of course.

Fairly recently more powerful LED’s have appeared. They are similar to metal halides in two ways – they come in a canopy and use electricity.

The makers of some canopies have claimed that the light output (the combined output of all the LED’s in the canopy) is equal to X watts of a metal halide, this being 150W, 250W or whatever – the more LED’s the more power. I am not a lighting expert but have noted some argument over this claim. However, contributors to the argument seem to agree that the output is close and is increasing as technology advances. The important point is that there are reef systems that are thriving under LED lighting.

There is another LED system available that is not a standard canopy. These resemble to an extent a fluorescent tube in shape, and can be purchased in different lengths and, again to an extent, different spectrum outputs. So, as with fluorescent tubes, different units can be combined over the aquarium.

LED’s do not need to be changed as regularly as metal halides, in fact they could last 20000 hours. That’s a long period of aquarium lighting, just divide it by the amount of time the aquarium lights are on each day. So there isn’t a requirement to spend money on new bulbs once a year or so.

The heat from LED’s in canopies is not directed into the aquarium as the canopies usually contain a fan to channel the heat away. In warm areas this will add to the work that air conditioning needs to do. Most aquarists will not need to purchase a chiller or employ fans to cool the seawater, which should remain more stable in temperature. The LED’s that are a little reminiscent of fluorescent tubes do not have fans – to be honest I am not sure of the heat output effect but would assume that it will not be great as each ‘tube’ often has less than ten LED’s present.

There isn’t a requirement for additional fluorescent tubes, so the aquarist misses that expense and the need to change the tubes once a year or less. This is because the LED’s incorporate both white and blue LED’s and, in the canopies at least, these usually can be timed on and off according to the aquarist’s wishes. In fact, in the more expensive canopies, the effect of a cloud rolling across the sky can be timed in.

Obtaining a metal halide system costs less than an equivalent LED canopy, and obtaining a fluorescent tube costs less than an LED ‘tube’. That is the problem at the moment with LED systems, the initial cost.

However, when the ongoing cost of a metal halide is considered against the same for LED’s, the LED’s show a considerable saving. In addition, the LED’s do not heat the seawater (at least not to the same extent) and permit the aquarist to maintain temperature stability more cheaply.

Importantly, LED’s are not so electricity hungry.

LED technology continues to move forward and it seems clear that if the current LED systems can be successful then ones in the future will be and better. It is now necessary more than in earlier days to be careful with electricity costs and it is doubtful if this is going to change significantly.

My own guess is that the future for LED’s is assured and the metal halide will begin to fade away before too long. The price of LED systems does need to come down though before LED’s become the usual lighting system considered by most reef aquarists.

If the system is fish only then lighting is important but nowhere near as much. Fish need to be able to see and the aquarist wishes to see them. That’s it. Of course, it is still desirable to have a dawn/dusk effect using at least two fluorescents, usually blue and white, with electric timers so that something approximating the increase and decrease of light at the beginning and end of the day can be provided. When should the fluorescent tubes be changed? If a tube is seen to be flickering then it needs changing. If the aquarist thinks the light has diminished it probably has, so get a replacement tube. If the ends of the tube(s) are blackened then it is getting old and could do with changing.

The reef system is a different matter. Here, lighting is usually fluorescent tubes, metal halide or a mixture of the two. As corals are being kept, be they soft or hard types, or a mixture, the lighting needs to provide the correct spectrum and intensity. When the lights are new they will do, but as time progresses the lights reduce in intensity and the spectrum can shift, both undesirable. The only way to correct these problems is to renew the light source.

When to renew is the subject of argument among experienced aquarists and particularly among very keen ones. Some argue that fluorescents should be changed as frequently as every 3 months and metal halide bulbs every 9 months. However, the guidelines for changing tubes and bulbs are more generous than that.

In the case of fluorescent tubes the point when flickering and blackened ends arises as previously mentioned should never be reached. The tubes should be changed well before that. The guideline is 12 months maximum from the date of first use. There isn’t a problem in changing the tubes more regularly than this of course and will not do any harm at all. I change my fluorescent tube array every 9 months.

Metal halide bulbs could be changed after a maximum 24 months from date of first use. This seems a long period and many aquarists, to be on the safe side, change more frequently. I do not use metal halide, but if I did I would probably change every 12 months. The expense is not too high. Changing the bulbs varies with different aquarists, some change at either 9, 12, 18 or 24 months! Just be safe by changing regularly at a shorter interval than recommended.

The recommendations for the expected life of a bulb, particularly metal halide, are usually available from the manufacturer. This is often given in hours so that varying lighting ‘time on’ periods can be accommodated. Once the recommended hours are known it is a simple matter to divide this by the daily running time so that life expectancy can be seen.

All aspects of marine aquarium husbandry require attention from time to time. It is essential to pay heed to one of the major ones, lighting. The use of a note book is recommended to remind the aquarist when a lighting change is due, and the notebook is useful for many other memory aids.

In a fish only system the lighting is not particularly important. The fish need to see and also be seen, that’s all. Two fluorescent tubes¸ one white and one actinic blue are sufficient. Two tubes are required in order to create a ‘dawn and dusk’ cycle. Of course, the aquarist could use more tubes if desired.

For the reef aquarium there are options. The aquarist could choose metal halide lighting¸ which is the most popular at the moment. This popularity is likely to change because halides are expensive to run and give out a lot of heat which can affect the seawater. The light of the future is the LED array though at present these are expensive to buy. They do not put heat into the aquarium and are much cheaper to run. There are also fluorescent tubes which have been available to aquarists for many years, which don’t develop the heat of a metal halide and are again cheaper to run.

Fluorescent tubes have developed over the years – T12 tubes, then T8’s, and then T5’s which are the current type. All types are still available though it is the latter one that is of most interest to aquarists. The numbers 12, 8, and 5 refer to the diameter of the tube.

The development of fluorescent lighting has included spectrum. Aquarists can choose tubes of differing spectrum. For example, a marine white tube will give a spectrum of around 10000K (K=Kelvin which is a measure of colour temperature). White is an important and much used colour in the aquarium. Another is blue actinic which is used by perhaps the majority of reef aquarists.

The reason why colour output is so important is because in the sea colours disappear at various depths – red disappears quickly¸ blue penetrates deeply so the corals are used to certain colours and require them (this is a generality). Within the flesh of most corals kept on a captive reef are zooxanthellae which are single celled algae. These algae require light of the correct type to flourish. This in turn means the coral will be healthy.

T5 tubes could be used for any coral as they can be obtained with the correct colour output. However, there is one more consideration and that is intensity.

Metal halides are powerful and can ‘punch’ light to the bottom of deep aquariums. T5 lights do not have as much ‘punch’ and this is the area where particular care needs to be taken. The aquarist who has decided to use T5 lighting should be aware of this limitation.

If the aquarist wishes to keep hard corals (SPS) then the aquarium needs to be shallow, or at least it does if the hard corals are to cover the reef. A depth of around 12” is probably the limit, though even then the aquarist will have to watch that corals lower down are settled. Not all corals require as much light so those that are happy with less can obviously be placed lower. It is probable that most success will be obtained in the top 6″ or 9″ from the surface.

Most aquarists will not be happy with an aquarium of 12″ or less depth. Most are 18″, 24″ or even more. If the desire is to have an entire reef of hard corals (SPS) then T5 lighting will not do, though blue actinic lighting can still be used.

If the aquarist wants to have a mixed coral reef, that is some hard corals and also soft corals, then T5 lighting could be used. As above the hard corals that need a lot of light will need to be placed in the top 6″ or 9″ from the surface. The rest of the reef can house corals that will accept less light such as many soft corals. Even so, the lower areas will be the place for corals that can settle with low light levels, there is a fair choice. Some aquarists do not like an arrangement as described as it could appear too stratified and unnatural. In this case the choice is really soft corals and those hard corals that can survive without high light intensity, though they will probably still require to be in higher areas of the reef.

Soft corals are generally easier to place, though once again care is needed to ensure that they receive sufficient light.

When fitting T5 fluorescent tubes it is advisable to use reflectors and to fit as many as possible lengthwise. These tubes need electronic ballasts and types that can drive two tubes are available which makes for more convenience. The tubes should be equally divided between marine white and actinic blue. Lay them out white then blue then white etc so that there is a good and even spread of both. If the tubes total an odd number, make the additional one a white. In addition the tubes should be fitted as close to the water surface as is practical to ensure maximum light availability. Creating a ‘dawn and dusk’ cycle is easy, just wire the blues and whites separately and make use of two electric timers.

T5’s are the latest incarnation in fluorescent lighting. The aquarist who makes use of them will have a good choice of lighting tube lengths and colours, and will also know that they are less expensive to run than metal halides. A number of tubes as described when housed in a close fitting hood generate quite a lot of heat so the aquarist should be aware of any effect this may have on seawater temperature, though any problem is not as great as with metal halides.

Success can be achieved with T5 lighting as long as the restrictions, mainly to do with depth of aquarium are taken into account. It is also important to change the tubes every 6 months to a year, the latest being a year. This is to minimize light intensity reduction and spectrum shift.

Life on the wild reef isn’t an exception. During the day many fish and other life forms are out and about finding food. As soon as darkness approaches they find a safe sanctuary where they can pass the night, as at night other life emerges, much of it predatory.

So life is tuned to a night/day cycle. So it is in the aquarium as the livestock need the cycle to function. I don’t know what would occur to daylight loving stock if the lights were left permanently on, or vice versa, but it isn’t an experiment I’d care to undertake.

Providing a day/night cycle is simple. Let’s start with a fish only system. This system type is not normally lit by metal halide bulbs, but by fluorescent tubes. For the cycle to work there needs to be at least two tubes, one actinic and one marine white. There also needs to be two electric timers.

Each tube is connected through its ballast to a timer. The timers are set so that the actinic tube switches on about ½ hour before the marine white. At the other end of the cycle, the marine white is set to switch off ½ hour before the actinic. The marine white can be left to run between 8 and 10 hours, meaning that the actinic tube will be on 9 to 11 hours. The fish will now wake up to a ’dawn’ and be stimulated to prepare for night at ’dusk’.

The reef system is very similar, except that lighting on a reef system is more critical and more lights will often be present. This does not make any difference to the lighting cycle system though. If a metal halide is in use, then an electric timer will be required for this. The metal halide is the main light for the day period. If marine white tubes are in use, they will need to be connected through one electric timer. If not already present, the aquarist will need to provide one or better two actinic tubes, which need to be wired through the other electric timer. Again, the actinics switch on and off ½ hour before and after the main lighting. The main lighting can again be left on between 8 and 10 hours, again meaning the actinic will be on for between 9 and 11 hours.

The lighting periods suggested above are not critical, and the aquarist can make the timing choice according to the needs of the livestock.

Sometimes it is recommended that the main marine lighting should be on for 12 hours. This recommendation relates to the average tropical day which is circa 12 hours. However, there isn’t a need for intense lighting for this length of time as it doesn’t occur in the tropics. Either side of midday the light is intense, but earlier and later it is less. In addition, the power of the sun cannot be equated in the aquarium.

If a lighting regime such as outlined above is implemented, the aquarist will perhaps be surprised at how quickly the fish ‘learn’, appearing a little after ’dawn’ and preparing for night at ’dusk’.

The lighting regime is also good as it is much more natural than plunging the aquarium into light or darkness, which is bad. The closer to nature’s dawn/dusk environment the system is the more contented the livestock will be.

There is an advantage to the aquarist too. Watching the fish react to lighting changes is one. Using a torch and watching the night life is another, though more for the reef system. The aquarist could be surprised at the amount of life and movement there is after dark.

The creatures seem to be attracted to light and they are very small. So what are they? Are they dangerous or not?

Have a look at the attached video, and if you have any idea then let us know in the comments facility. Or, if you prefer, by Email.

Here’s the video…