Reef Ramblings

Check out this fascinating, somewhat psychedelic, video of a night dive in the Red Sea shot under ultraviolet (UV) light, showing all manner of reef organisms exhibiting fluorescence. Animals including corals, fishes, echinoderms, and even the shell of a hermit crab show off a wide range of bizarre colouration.

Look out for the Scorpionfish and Pipefishes in particular.

In some of the sequences it’s particularly interesting to see the large quantity of zooplankton zipping around the reef, demonstrating how poorly our reef aquariums replicate the wild reef.

There’s a nice sequence of a family of clownfishes in their host anemone, which also shows large numbers of juvenile Dascyllus trimaculatus, Threespot Dascyllus or Domino damselfishes, sharing the safety of the anemone.

Also watch for the images showing Xenia species, Pulse Corals, happily pulsing away at night.

Fluorescence

Fluorescence is the result of a material absorbing one wavelength of light, re-emitting it as another, usually at a longer wavelength. The visible wavelength of light ranges from around 400 nm, blue light, to around 700 nm, red light. The UV light used in this video is UV-A and is in the range between 315 nm and visible light, probably around 380 nm. This makes the fluorescence produced even more remarkable as the UV light used is invisible to the human eye, yet we end up seeing these higher wavelength, visible colours.

You experience this phenomenon when you observe your aquarium under blue light alone, as most aquarium blue or ‘actinic’ lamps have a spectrum that reaches down to around 380 nm hence emitting UV-A.

UV light in this range is a useful tool for detecting newly settled juvenile corals in the reef aquarium; although newly settled corals are small and difficult to see, the fluorescence that they emit can make the easy to find.

See also, Coral magazine, Vol.5, No. 3, ‘Fluorescence’

Tim Hayes

Reef Ramblings

©2012-12-05

Welcome to a new series of articles aimed at those aquarists concerned about the costs of running their reef tanks. Your concerns may be purely about the financial cost of running your reef or you may have wider concerns regarding the carbon footprint of your reef, either way, in this series of articles I’ll be looking at how you can make economies that will effect both areas of concern.

All of a sudden times seem hard, food prices are up and energy prices, both electricity and petrol, have risen substantially in a short period of time. You’re feeling the pinch and may be worrying whether you can continue to afford to run your reef.
The question is what should you do? If you pack your reef in you’ll make a large monetary loss, as you’ll never realise the full amount of money you’ve spent on it over the years. But you can make your existing reef more energy efficient and cheaper to run by reviewing the equipment you’re running.
You can also save money by reviewing the kind of reef you keep and by looking at the way you feed and maintain your reef.

Although I’m going to cover lighting in a future article in this series, I am going to briefly touch on the subject in this first introductory article.

Do You Really Need All That Light?

The cost of lighting a captive reef is often the greatest expense reefkeepers have to contend with. There are two expenses involved here, the cost of replacement lamps, the cost of the electricity consumed by the light. On top of this there may also be the less obvious cost of managing the heat build up, resulting from the level of lighting used. This heat build up often necessitates the use of chillers, or other means of cooling, to maintain a safe temperature within the aquarium.
Guess what?
That additional cooling can be as much as your lighting bill if not more!

So What to do?

There’s been a trend over the last few years to use more and more light over reef aquaria, the question is whether it’s really necessary. If faced with the choice of having to give up your reef as it’s becoming too expensive to run, why not consider scaling back the amount of lighting used?
Just remember, there’s no “best” level of lighting, just the level of lighting appropriate to the species being kept.     If you’ve been keeping SPS, maybe consider selling them or trading them, and then change the theme of your reef, making it into a soft coral or LPS reef. LPS corals and soft corals are often found in lagoonal conditions where the water may be turbid, hence they can be maintained happily under lower levels of lighting than required by SPS corals such as Acropora.
There are many different types of reef and these can be split into many different zones. If you need to reduce the amount of money you’re spending lighting your reef tank I’d suggest doing a bit of research into these different forms of reefs and the different zones that they can be split into. I’m pretty sure you’ll be able to find something that will suit you and save you money by reducing your electricity bill.

For coral information I’d suggest: Aquarium Corals by Eric Borneman.

For more book recommendations see my review of reef aquarium literature.

Any questions or comments, please feel free to get in touch with me: tim@midlandreefs.co.uk

Tim Hayes
Midland Reefs
©2008

An Introduction to PAR.

There are far more things to bear in mind regarding lighting than was covered in Lighting Basics. In this article I thought I’d discuss the shortcomings of the human eye as an instrument for assessing lighting and at the same time introduce the concept of assessing lighting in terms of PAR.

In places this is a far more technical article than Lighting Basics but please try to stick with it. Lighting is a very large subject but an understanding of how light works in the natural environment and in the reef can be very useful in making you a successful reef aquarist. One aspect that is rarely covered in reef aquarium literature is that of colour perception, this is looked at here in terms of human colour perception, a future article will examine how and why the colours of reef animals appear quite different in their natural environment.

The Human Eye is Not a Good Judge of Light Output.

When you go to your local store and say, “I’ve got more light than that over my tank at home!”, unless you do actually have a set up with multiple 400w halides, or triple 1000w lamps (this is not an exaggeration! I know German hobbyists who use this amount of light over their home reef!), the chances are you eyes are being fooled. In a marine aquarium shop there’s one heck of a lot of light, with all this light as background when you look into a shop’s display tank, often it’ll appear as though it’s not actually that bright.
At home the lighting over your reef tank is probably the brightest, most powerful lighting you have in your home, with the possible exception of security lights. When you contrast the low background lighting against you “brightly lit” reef it’s no wonder it looks bright.

The human eye is constantly adapting to the amount light it’s experiencing. Over time, your aquarium lamps are slowly dimming as they age but unless they reduce light output in a short time to such an extent that they become markedly dimmer, your eyes won’t be able sense the difference in light output.

Most aquarists light their aquariums in response to aesthetics rather than the requirements of their corals. This leads to many an argument about which is the best make of lamp or the best colour of lamp to use. And again brings us back to the deficiency of the human eye as a measuring device as, unfortunately, the perception of colours, in particular blues and greens, can vary significantly from individual to individual (S. Ings 2007).

Light is electromagnetic radiation; it varies in wavelength and intensity. The light we see, visible light, typically ranges from around 380 nanometres (nm) to 710 nm but there is some variation person to person at each end of this range. This is the range of wavelengths producing the familiar spectrum of colours seen in a rainbow – Violet • Blue • Green • Yellow • Orange • Red. The blue end of the spectrum being of shorter wavelength than the red end of the spectrum. Beyond each end of this spectrum there’s electromagnetic radiation that we can’t see but that will still have an effect on the animals we keep in our captive reefs, most notably ultraviolet (UV) radiation (200 nm – 400nm). As an approximation you can use the following as a guide to colour and wavelength, though do bear in mind that that the spectrum is continuous, blending from colour to colour with no strict delineation.

Violet 380–450 nm
Blue 450–495 nm
Green 495–570 nm
Yellow 570–590 nm
Orange 590–620 nm
Red 620–750 nm

Human Colour Perception.

The human eye achieves colour perception through three types of colour receptors or cone cells, each of which contains pigments sensitive to different ranges of the spectrum. This is termed trichromatic colour vision. Incidentally, some marine animals have four types of receptors, the extra receptor conferring vision into the UV range – something I’ll come back to in a future article.
In the human eye these cones are respectively, receptive to: short wavelengths of light between 400 and 500 nm with a peak sensitivity of around 420 nm, medium wavelengths of light between 450 and 630 nm with a peak sensitivity of around 534 nm, and long wavelengths of light between 500 and 700 nm with a peak sensitivity of around 564 nm. Overall this gives a peak sensitivity in the yellow region of the spectrum. As I’ve mentioned throughout this article the human eye varies in its sensitivity and in individual perception of colour, so as you may have guessed, the response of these cones will vary from person to person, even those with normal colour vision.
Given the above information this might explain why some aquarists will complain of lighting looking too yellow or green for their tastes

Kelvin Rating.

Lamps are available in a number of different Kelvin ratings and it is this rating that gives us a guide to the colour of a given lamp. For reef use we start at around 6500˚ K and progress upwards through 10000˚ K, 14000˚ K, and end up at 20000˚ K. The 6500˚K is roughly equivalent to daylight, representing the colour spectrum of light at midday, and is ideally suited to corals that would be growing in very shallow water. As the number representing the Kelvin rating increases, so the light produced will appear to have an increased blue colouration. There are two ways this can be achieved, either there is an increase in output of light in the blue portion of the spectrum or there is a reduction in the output of light in other portions of the spectrum.
When using lamps of increasingly higher Kelvin rating, the increase in the proportion of blue light along with a reduction in output in other areas of the spectrum mimics what happens to light as it penetrates deeper into the sea.
As depth increases, the water takes on an increasingly bluer caste. This is due to the longer wavelengths of light, starting with 700 nanometres (red, moving through orange, then yellow, and so on) being progressively filtered out by the water. Red and orange will have been filtered out within five metres of the surface, yellow by about ten meters, green by sixteen meters, leaving only blue and violet. The removal of these wavelengths of light affects the appearance of all these colours giving a completely different picture to that seen under white light. A reefscape at around twenty five meters depth would, under manmade lighting, be dominated by bright shades of red, pink, and orange (as we’d see it under regular tank lighting), but in reality it’s made up of shades of green, blue, violet, and, colours in the ultraviolet that we can’t perceive.

Intensity.

Generally speaking intensity is governed by the amount of watts a lamp consumes, So, as a rule of thumb with all of the traditional forms of reef lighting, the more watts the greater the light output. But how efficiently is this energy being employed? As mentioned in the article on Lighting Basics a well-designed lighting unit can outperform one of significantly greater wattage. So how do you identify the better performing unit?

PAR – Photosynthetically Available Radiation.

While PAR might be an unfamiliar term in comparison to the more often seen Lumens or Lux, it is by far the most appropriate way for us to assess light in connection with the reef tank.
Lumens and Lux are measurements of how bright a light source appears to the human eye and as such has little relevance to the reef aquarium. Since the human eye is most sensitive to colours that are of little interest in a reef application, has a lower sensitivity to the ones that we are interested in, and, as discussed throughout this article, varies widely in its perception of colour, Lumens are of little use as a means of assessing lighting for the marine aquarium. If a marine lighting lighting manufacturer rates his lamps’ output in Lumens you’re only being told how bright the light will appear to you and how much it’ll light up your room, not how well it’ll be utilised by your corals. I’d also reflect that any manufacturer, aquarium salesman, or expert going on about Lumens is displaying an ignorance of the subject.

The unit of measurement for PAR is micromoles per second per square meter, a measurement of how many photons of light strike an area per second. Don’t worry over much about this esoteric form of measurement, for reef usage most of just refer to a reading in PAR. So to illustrate the sort of figures we’re talking about, a reading at the ocean’s surface at the equator at midday is reported to be 2000 PAR. Referring to the work of respected reef lighting researcher Sanjay Joshi, in the reef aquarium we need a PAR reading of about 200at the surface as a minimum requirement for small polyped stony corals – SPS, that’s Acropora, Montipora, Pocillopora species and the like. If you’re getting a PAR figure of 150 at the bottom of your aquarium then you’ll have enough light to pretty much grow anything. This quantity of light available to your corals, the sheer power output, is the most important aspect of lighting.

I believe that a PAR meter is an item of equipment that all serious reef aquarists should own – and use … At Midland Reefs we use Apogee PAR meters, they’re inexpensive compared to other meters available for scientific or laboratory work but for reef use they’re ideal.
As the sensor is submersible it allows you to measure the amount light that’s actually reaching your corals. This in turn gives you the information you need when positioning or repositioning your corals to ensure that all the various species are receiving light that’s optimum for their requirements. When you purchase new corals you can get a reading from the dealers display tank then, when positioning the coral in its new home make sure that it’s not receiving significantly more light that could lead to photoshock, possibly resulting in bleaching.
Whenever you replace a lamp take a PAR reading at a known distance after running the lamp for around one hundred hours (this is allow the output time to settle down). Record this reading, along with the distance it was taken at. Periodically you can then re-check the lamp to see how it’s performing, eventually when you get a reading that’s thirty per cent less than the original one you’ll know it’s time for a replacement. When you do replace the lamp take a reading then adjust the height of the lighting unit above the water (raising it higher) so that the same amount of light is hitting the surface of the water as with the old lamp. Over the days that follow you can then incrementally lower the lighting unit letting your corals safely acclimate to the increased output of the new lamp. This is a routine that would also be applicable if you were to up rate your lighting system to something with a significantly greater output, say going up from 150 w halides up to 250 w halide. Following this procedure you know when to change your lamps, rather than just guessing, avoiding the possibility of changing prematurely. It gives you the option of adjusting the height of your lighting to compensate for reduced output over time. And, also, gives you endless opportunities to assess improvements in your lighting through the use of different lamps, ballast, and reflectors.

Incidentally, one consequence of using higher and higher Kelvin rated lamps it that of less light output. As the Kelvin rating increase the light output reduces, so a 10000˚K lamp produces less PAR than a daylight rated lamp of 6500˚K, a 14000˚K lamp produces less PAR than a 10000˚K lamp, and so on.

Any questions or comments, please feel free to get in touch with me.

Tim Hayes
Midland Reefs
©2007

This first in a series of articles on lighting is aimed at people new to the hobby who may be a little confused by all the lighting options available to illuminate a marine aquarium. Some of this may appear simplified to more experienced aquarists but, hey! We’ve all got to start somewhere! See elsewhere on the site for articles that go into lighting in greater depth.

Why light the aquarium in the first place?

The majority of the animals, the fishes and invertebrates that we keep in the reef aquarium, come from the tropics where the midday sun can be extremely bright. One adaptation to this abundant light is that many species of invertebrates, in particular the corals that we keep in our aquaria, have adapted to a way of life that involves a symbiotic relationship with single celled plants that convert sunlight into energy to the benefit of their host through the process of photosynthesis. So, to successfully maintain these animals in captivity we need to provide them with a comparatively large amount of light.

Types of lighting:

Although there are a number of different types of lighting that can be used in the hobby there are a few things that they all have in common. They all produce light and to a lesser or greater extent they all produce heat. Lamps are rated in terms of watts to give an indication of their power output and energy consumption. Additionally, lamps used for aquatics have a Kelvin rating e.g. 6500˚K, 10000˚K, 14000˚K, 20000˚K. This is a description of the colour of light the lamp produces in much the same way as domestic lights get rated as being, “warm white”, “white”, or “cool white”. This is often also referred to as the spectrum of the lamp. To an extent the choice of Kelvin rating used over a reef tank is down to the aesthetics of the aquarist – the colour that gives the effect that the aquarist finds most pleasing. Going from 6500˚K, through the intermediate ratings, and up to 20000˚K will give an effect similar to that of how colour changes with increasing depth. At the time of writing there seems to be trend to use around 14000˚K in the UK and Europe, with many aquarists in the US going for the far bluer colouration of 20000˚K. There is variation in colour between lamps of the same Kelvin rating produced by different manufacturers so the choice is somewhat subjective. Anything between 10000˚K and 14000˚K will be fine for the majority of corals you’re likely to keep as a newcomer so don’t worry about it too much.

Note: There often seems to be a perception that the bigger the Kelvin number is the more powerful the light. The Kelvin rating refers to colour, while wattage indicates power.

(For a more in depth examination of Kelvin rating and water depth, please look out for a further article on this subject)

Lamp Fitting Designation.

All the different types of lamp have some sort of designation to describe what lamp fitting each particular lamp is suited to e.g. T8, T5, RX7s etc, These fittings are standardised so a lamp designated, say RX7s (150w metal halide lamp), no matter who the manufacturer is, will fit any RX7s fitting.

Remember: Just because you have a lighting unit that’s made by a company such as Arcadia, it doesn’t mean you have to replace the lamp with an Arcadia one. Any lamp with the same type of fitting can be used in that unit.

Fluorescent lights.

These can be split into 2 categories, linear fluorescent lights – the familiar fluorescent tube, and PL lamps or power compacts – also sometimes referred to as energy saving bulbs.

Linear fluorescent lights can vary in length, wattage (usually proportional to the length), fitting –T12, T8, T6, T5, etc. and Kelvin rating. There are also different outputs of fluorescent available: NO (normal output), HO (high output), and VHO (very high output) but with the exception of T5 lights these are not seen often in the UK. Regarding T5 lights, beware if you’re trying to put something together on the cheap; the lights produced by reputable aquatic manufacturers will essentially be HO lights, whereas the majority of T5 lamps you see at low prices in the DIY shops are NO lamps and will produce less light. Not really recommended for aquaria deeper than 45cms (18 inches).
Multiple lamps are required to provide sufficient illumination for a reef and, to get the best out of them, they need to be close to the surface of the water. This can present problems when it comes to accessing the tank to carry out maintenance and also brings with it the potential for overheating the water if the top of the tank is enclosed.

T5 lamps usually have a greater power output than T8 lamps but have the downside of running at a higher temperature, which in turn may influence the running temperature of the aquarium.

PL lamps or compact fluorescents are in effect a linear lamp that has been either folded back on itself or looped round in perhaps a spiral. Fittings here can vary quite a bit but the most common ones for aquarium use have either 2 or 4 pins in a straight line. Watch out for cheap (inferior) imports, mostly of Chinese origin, where the lamps have the 4 pins arranged in a square – you’re unlikely to be able to find any quality lamps with a spectrum suited to aquarium usage to replace these with when they, almost inevitably, fail.

Power Compacts have the advantage of producing more light in a smaller area due to their configuration, the downside here is again heat, plus their shape means that the reflector cannot be used as efficiently so they may produce less light than a linear lamp of the same wattage.

It is possible to compensate for the lower output of fluorescent lighting by extending the photoperiod, that’s the length of time the aquarium is lit to represent a tropical day. A day length of 12 to 14 hours is acceptable.

Metal Halide (MH) Lighting.

Metal halide lighting (sometimes also referred to as HQI lighting) is currently the gold standard in reef aquarium lighting. These lights throw out a lot of light and also a lot of heat, aquariums utilising multiple MH lighting units often need the addition of a chiller to keep the water down to a temperature suitable for corals. Available in wattages ranging from 70w, through 150w, 250 w, and 400w, up to a crazy 1000w!! 70w is not much used and is a bit on the low side, 150w is very common but probably best thought of as entry level MH lighting, 250 w is a great choice for most usage, 400w is probably best employed over deeper than average tanks, and while 1000w is more the preserve of public aquarium systems, that’s not to say that hobbyists don’t go to this extreme – I know of hobbyist tanks that are lit with three 1000w MH lights!

Aquarium MH lighting units (or luminaires) are generally ugly and heavy items of equipment that need to be suspended from the ceiling above the tank. They offer light penetration to a greater depth than fluorescents and are probably better suited to maintaining corals because of the “glitter lines” they produce, emulating the same effect as the sun produces in the wild. Glitter lines are the ever-changing patterns of light and shadow you see on the base of the aquarium (much the same as you see in shallow water at the beach). You get these with MH lighting as the light is a point source the same as the sun, this effect gives the reef aquarium a far more dynamic appearance with shadows being well defined; fluorescent lighting is a diffuse light source and you’re unlikely to get glitter lines without fairly extreme surface agitation. The situation is slightly better with power compacts as they are put out more light in a smaller area than linear lamps.

Other advantages of MH lighting over fluorescents include retaining access to the aquarium for maintenance, the fact that the lights are further away from the water surrounded by air which will, to a certain extent, mitigate the problem of heat transfer.

Keep the cover glass protecting the bulb clean to optimise light output. A build up of salt from minor splashes will soon reduce the amount of light reaching the aquarium.
Don’t run lamps without a cover glass or you may end up exposing your corals to excess UV radiation, which could cause them to bleach.
Manufacturers specify a minimum distance for the light to hung above water level as a safety precaution: water splashing against the hot cover glass, perhaps at feeding time, may cause the glass to shatter

The Components of a Lighting System.

So far I’ve talked about lighting as a whole but an aspect of lighting that’s not as well appreciated as it should be is that any lighting system is the sum of 3 separate factors. Lamp, ballast, and reflector all contribute to the overall efficiency of any lighting system. If each of these elements has been optimised to work well with the other 2 then you’ll have a great lighting system, but one inferior element may mean you could be actually producing less light than a well put together lighting unit of a lower wattage. It’s quite possible to put together a single 250w MH light that will out perform an off the shelf 400w unit of inferior design.

Reflectors.

A reflector is essential to make the most of the light emitted by your lighting system. This is mostly applicable to fluorescent lighting where the separate components are often bought separately – don’t forget to install reflectors, particularly in Juwel conversions and the like.

In the UK most aquarium lighting systems used, especially MH ones, are complete packages put together by the manufacturer. It’s worth noting that nearly all of these MH units are compromised by the small size of reflector that is used.

Keep reflectors clean to optimise light output.

Ballasts.

The ballast is the box of tricks that makes the lamp light up. There are 2 types of ballast on the market, electromagnetic and electronic. Electromagnetic ballasts are the traditional method of lighting lamps; they tend to be heavy and waste energy in the form of heat. With fluorescent lighting, an inefficient ballast can consume almost as much electricity as the lamp itself so don’t be fooled into thinking that your 36 w lamp is only using 36w, it may be using say, another 30w, meaning your “low wattage” 36w lamp is actually using 60w or more!

Electronic ballasts are a more recent introduction; they are lightweight and far more efficient, consuming only a few extra watts of electricity, produce less heat, and extend the life of the lamp. They run much cooler than traditional ballasts. I have electronic ballasts that run at a low enough temperature that you can comfortably rest your hand on them, contrast this with electromagnetic ballasts that may run at around 120˚ Celsius, ouch!
It’s worth noting that some T5 lamps need to be run with electronic ballasts otherwise they won’t light.
There are also high-frequency electronic ballasts available that can give an increase in power output of around 10%.

Much of the above refers to fluorescent lamps, but there are also electronic ballasts available for MH lamps, which offer similar improvements in performance but the energy saving is not as marked as it is with fluorescents.

Lamps.

Lamps, bulbs, tubes, whatever you want to call them – different manufacturer’s lamps will perform differently when run with different ballasts. This is an area where a little experimentation may pay off to find the lamp that is best suited to your ballasts.

Lamps don’t last forever. It’s good practise to replace them when the output has reduced by 30%. A rule of thumb would be to change lamps yearly but as a number of factors influence how quickly lamps deteriorate I must stress that this figure is just give for guidance. A more accurate way of determining the life of a lamp would be to measure its output with a PAR meter. (For more on PAR and PAR meters, please look out for a further article on this subject).

Be careful handling MH lamps with bare hands as secretions from the fingertips may cause bulb failure.
Double ended MH bulbs should be fitted with the inner exhaust tip pointing upwards (the small piece of glass sticking out of the inner bulb where it was sealed at the factory).

MH lamps should be allowed to cool down for a few minutes after being turned off, before they are re-ignited.

Actinic and Dusk / Dawn Lighting.

Blue lighting is often referred to as actinic lighting; it’s been common practise to run these lamps in addition to regular lighting to bring out fluorescence in corals. This practise is probably not necessary with today’s lamps, as they should be generating plenty of light in the correct part of the spectrum to fulfil this requirement.

Where these blue coloured lamps do come in useful is as a way of producing a dusk / dawn effect by having them come on half an hour to an hour before the main lights and then going off a similar length of time after the main lights have been extinguished. This goes someway towards replicating the natural dusk / dawn effect and also prevents animals from being spooked by being suddenly exposed to something roughly equivalent to the midday sun or by being suddenly plunged into darkness at the end of the day.

Note: With all lighting it’s important to employ timers to ensure a regular photoperiod for you reef.

Above all, please remember that there’s no “best” lighting for a reef tank – only the lighting most appropriate to the animals being kept.

Any questions or comments, please feel free to get in touch with me.

Tim Hayes
Midland Reefs
©2007