Do You Have To Have Metal Halide Lighting For Hard Corals?

Many reef aquarists see hard corals as the height of achievement and the closest thing to a real coral reef in captivity. This isn’t quite true of course, as parts of coral reefs are dominated by soft corals. Nevertheless, a hard coral reef can be very beautiful, and if the aquarist has selected the corals for shape and colour carefully it makes a stunning picture.

The very first requirement for a successful hard coral reef is seawater quality - it must be high and consistently so. This includes the necessary levels of calcium, alkalinity etc. Water movement must also be appropriate, and hard corals generally prefer considerable movement, more so, again in general, than the soft corals.

The second requirement is appropriate lighting. This should be of the appropriate power, which is measured in watts (W) and also the appropriate spectrum. With spectrum, metal halide bulbs are usually purchased with a Kelvin (K) rating. Kelvin is a measurement of colour temperature. The perceived colour of the bulb will become more blue and colder looking as the Kelvin rating increases. For example, a 6500K bulb will appear more yellow than a 20000K bulb, which will appear more blue, or colder looking. Nowadays, it seems there is favour with the 14000K bulb, though the best Kelvin rating for corals is still argued over.

It should be remembered that the corals harbour symbiotic algae known as zooxanthellae. This algae is important to the corals so it is necessary for it to thrive. Zooxanthellae need light of the correct type so that they can photosynthesise. Current thinking is that blue light of the correct wavelength is needed. This seems reasonable, as much light of other colours is lost as the depth of the sea increases. Blue is nearly the last remaining light at depth and must therefore be available to the zooxanthellae in the natural habitat.

So, getting back to the point. Excluding power LED’s (now becoming more available) which are very expensive, there is really only one other light type that could be useful with hard corals, and that is the T5 fluorescent tube. These tubes come in various spectrum outputs, and the two that are of most interest are the marine white and actinic blue types. They should be fitted with reflectors and as many as possible placed over the aquarium, with an equal number of actinic and white if possible.

T5 tubes can produce the correct spectrum, but there is another problem, and that is light penetration. To be fairly sure that hard corals will be adequately lit, the tubes need to be fitted as close as possible to the water surface, maybe two or three inches away. This is quite safe with the fittings used nowadays. Even so, light penetration may not be adequate to any depth, and the corals could need to be sited in the top third of the aquarium (the top third being subject to the overall aquarium depth of course). Some adjustment of the coral’s position could well be required as time progresses.

It is feasible to have a reef such as described in the previous paragraph, with corals that are happy with less light lower down. If the aquarist selects carefully, then many soft corals could be used, but it is necessary to check that these corals are not going to be detrimental to the hard corals. This is because some corals use weapons such as sweeper tentacles which sting, and some soft corals use chemical warfare.

The metal halide bulb has more power (W) and therefore more penetrative ability. The light produced reaches corals lower down. There are guidelines on the power needed for different depths, to provide light for light loving corals. These are guidelines, not rules:

150W 10″ (circa 25.5cm)
250W 14″ (circa 35.5cm)
400W 22″ (circa 56cm)

While we’re at it, another guideline - a metal halide bulb can light around 36″ (circa 91.5cm) of aquarium, that is, 18″ (circa 45.75cm) each side of its centre. So a 72″ (circa 183cm) aquarium could need two bulbs placed 18″ (circa 45.75cm) in from each end. Again, these are guidelines.

As can be seen, ideally the depth of tank needs to be taken into consideration in the planning stage. There are other factors that can affect light penetration but the above is a general guide. It does not mean that a coral will not grow below the stated penetration point - the growth rate could be slower or the coral could be selected by the aquarist to suit the light conditions. (We’re back to that word again - research.)

Some aquarists fit, and many manufacturers provide, actinic fluorescent tubes to be used with the metal halides. Many aquarists consider it advantageous to do this. There is argument over the necessity of it - what if the Kelvin rating of the bulb is high and into the blue range? However, to my knowledge anyway, the additional fluorescent tubes don’t do any harm and seem beneficial.

There is another point that needs to be mentioned about metal halides, and the word ‘point’ is the point. (Err, I’ll tie myself up soon!) Because a metal halide bulb is a point source for light (a fluorescent tube emits light over its full length), a lovely ripple effect is created within the aquarium, much like the sun would create on the wild reef. There is argument about the importance of this among advanced aquarists, but it is enough to say that it is an advantageous effect, at least it is to me.

Two important disadvantages of metal halides are first, that they are expensive to run, and second, they can overheat the aquarium water. So before a final decision is made, consideration must be given to the cost in electricity and also to the environment the aquarium is subject to. If it is a naturally warm environment, there could be a need to invest in a chiller (seawater cooler) which in itself is quite expensive to purchase and fairly expensive to run.

Overall, the metal halide is the light of choice for a hard coral reef at the moment. As said, fluorescent tubes can be used, with extra care exercised by the aquarist.

Anyone planning a reef aquarium should be aware that the more than probable reef light of the future is the power LED array. This is expensive to purchase at the moment, but the aquarist may wish to check on the current situation.

---

If you're new here, you may want to subscribe to our RSS feed. Thanks for visiting!

Tags: Aquarium Lighting, Equipment, hard corals, metal-halide, sps-corals

Is There Such A Thing As The Best Aquarium Filter?

Filtration in the marine aquarium supports the number one requirement, and that is water quality. Whether the system is a fish only aquarium or reef aquarium, water quality is paramount. The next most important requirement is lighting for a reef aquarium.

The question here is a little too general. Are we talking of bio-filtration, or is it mechanical and chemical filtration? I don’t know what was behind the question so let’s have a look at them all.

Bio-filtration is the major filtration need in an aquarium, so let’s start with that. Bio-filtration is where the nitrogen cycle, or part of it, takes place. That is, bacteria take dangerous waste such as ammonia and nitrite and convert it. Without this natural service keeping a marine system of any type would be difficult, expensive and not so good for the inhabitants.

The major requirement for bio-filtration (at least the initial stages of the nitrogen cycle) is oxygen. So for anything to operate well this oxygen supply is required.

The first method with this in mind is the trickle tower, where water runs down with gravity through media. This is a good method of filtration, as oxygen is readily available from the atmosphere. The bacteria are not going to have any problems. The downside is that these filters produce nitrate and that point is the end of the nitrogen cycle.

So what about that old and well trusted method, the canister filter. These filters are very reliable and the modern ones are easier to service (this used to be a bind). The bacteria are completely submerged and depend on oxygen from the seawater, so it is important for the system designer to bear this in mind, that is the water surface should be open, and in addition if possible weirs should be incorporated, or a powerhead could be directed at the surface. Additional oxygenation may not be needed in a well designed system with correct water movement. Again, the end product is nitrate.

The under gravel filter is subject to the same oxygen considerations as the canister. However, the under gravel filter is, at least in my opinion, not a good choice because of eventual problems with media blockage. This filtration will not be considered further.

Though there are other bio-filtration methods the last one to be considered in this text is live rock. Live rock is natural in that it is nature’s product. The bacterial process in any filter type is natural of course, but live rock is natural overall. Live rock in sufficient quantity and of high quality can successfully filter an aquarium. A big plus is that this method can deal with nitrate if not abused - in other words, the filtration provides the full nitrogen cycle. That is a big plus. In addition, the very fact that it is rock means that the aquarist can use it to aquascape the aquarium, and it doesn’t matter if the system is fish only or reef. The bacteria again rely on the oxygen in the seawater, so the points noted about this are relevant.

It doesn’t take a detective to discover the champion bio-filtration system here, and yes, it is live rock. The downside is that live rock is expensive, and corners should not be cut to save money with this filtration. If money is a problem, then consideration to the canister and trickle methods can be given, remembering the point about nitrate.

Right, that’s that bit covered. What about mechanical/chemical filtration? There’s not much to be discussed here.

With this filtration the aquarist requires a method that is unobtrusive and reliable. There aren’t any oxygen considerations. The canister filter is the one, and ideal for the job. They usually have compartments where different media can go - sponge of various densities and other fine filter types to trap detritus, and carbon if used. As said, canisters are easier to service nowadays than they used to be and that is the main requirement - they should be regularly serviced and any carbon changed, and detritus trapping media cleaned or renewed. The cleaning can be under a tap, there isn’t any need for caution in respect of bacteria. (Note that this is mechanical/chemical filtration. If a canister is being used for bio-filtration then cleaning under a tap the media supplied for the bacteria is a no-no, as the bacteria will be killed with dire consequences.)

So there we have it, the best: live rock for bio- filtration and canisters for mechanical/chemical filtration. This is of course my opinion, but I would hazard a guess that there aren’t many who would disagree.

---

Tags: Aquarium Filter, Aquarium Filtration, deep-sand-bed, Equipment, live-rock

The Protein Skimmer - What Is Wet And Dry Foam?

In a saltwater aquarium there are various devices that are designed to assist in the maintenance of high quality seawater. Perhaps the most useful of these is the protein skimmer (ignoring bio-filtration).

As with all devices for it to be at its most effective it must be adjusted correctly. First though, the skimmer must be appropriate to the size of the system.

The normal way of sizing a skimmer is to simply double the net gallonage of the entire system, then find a skimmer that can deal with about that amount. This is a guideline only, and is designed to overcome the sometimes optimistic claims of manufacturers. As long as the skimmer is not a long way short of the guideline it should suffice. Having said that, some manufacturers seem to be more realistic of late with the potential performance of their skimmers.

Skimmers are available as ‘hang-on’ and stand alone, and it is the aquarist who decides which is the most practical. For example, if there isn’t a sump then a ‘hang-on’ is probably the best choice.

It is also important to ensure as far as possible that the model chosen is a good one. Internet forums are useful for this, though there are likely to be some differences in opinion. Maybe more useful, sometimes a local retailer has hobby-sized skimmers running on aquariums, and these can be judged quite easily. First of all, look at the chamber where the bubble/water interaction takes place. The bubbles should be very small and in very great numbers - the bubble chamber should be full of them and coloured white (ish). One respected manufacturer states that the important things about a skimmer are ‘design, air output, air output, and air output.’ Also look at the collection cup, hopefully the skimmate (the dirty liquid inside) will be dark coloured. (This colouration has a lot to do with the way a skimmer is set-up and the amount of dissolved organics available, so a visual check is not entirely reliable.)

So the foam. This is the foam that forms at the surface of the bubble chamber and rises up the throat towards the collection cup. In a badly set skimmer, foam rises very rapidly in the throat and dribbles nearly continuously into the collection cup. The foam can be seen to collapse immediately or nearly so. The skimmate collected is weak in colour and thin. The cause of this is usually the bubble setting, where the amount of bubbles being produced is too high. This is the so-called wet foam.

At the other end, the foam may not rise very much at all, but when any gets into the collection cup it is thick and dark. The foam can be seen to be stiff, and is very slow to collapse. In this case, the setting is not far from being correct. This is the so-called dry foam.

The general ideal is where the settings produce many bubbles, but the foam does not get into the collection cup all the time. The foam may rise up the throat only to fall back when the rise begins again, and it is stiff and not too quick to collapse. When dissolved organics are present, the foam rises and enters the collection cup readily. It is dark, thick and can be smelly.

The manufacturer’s instructions should be followed initially, setting the device as suggested. Make sure the foam does not flow into the collection cup too rapidly, but allow the skimmer time to settle for a few days, as foam production is often affected by the manufacturing process. Once this time period has passed, trial and error will show the best settings for an individual aquarium. There needs to be good bubble production, which is controlled by the air intake setting, balanced with the appropriate flow rate.

A skimmer does not usually produce skimmate continuously, but will react to any dissolved organics. Some additives cause a reaction, and the addition of foods, such as some frozen types, usually will too.

Once the settings have been arrived at, usually they can be left alone. It is important to clean the throat (and collection cup) of the skimmer, as the sludge in the throat will adversely affect performance. When cleaning is done, skimmers often needs a short settling period again before full performance returns.

---

Tags: Aquarium Water, dissolved organics, Equipment, foam fractionation, Protein Skimmer, Water Quality

What Is PAR?

When this topic arose I wondered what to do with it. The reason I wondered is that this website is designed for beginners and ‘earlier-on’ aquarists (though I notice that experienced aquarists are now visiting, and they’re more than welcome). Lighting is a scientific and technical subject.

Most things can be broken down to basics though, and an attempt has been made to do this. In addition, advice is always given to employ the proper lighting, that is spectrum and power, particularly for reef systems. Perhaps a basic explanation of PAR will demonstrate why this is, and is therefore relevant.

There isn’t a requirement to know any more than the need to employ the proper recommended spectrum and power output over a reef. Fish only systems are not so demanding of course, the fish need to see and be seen, and it is good to see the colours reasonably enhanced.

Having the proper spectrum and power output is important, as said. The power output is measured in watts (W), and with metal halide bulbs this requirement depends on the depth of the aquarium. Fluorescent tubes have power outputs generally relevant to their length, though different tubes exist (eg. normal output (NO), high output (HO), and very high output (VHO)). Spectrum refers to the colour of the light, which is of particular importance to the corals, or more correctly a great many of them. The corals that we have in our aquariums for the most part require the correct spectrum.

Generally, corals contain zooxanthellae, or single-celled symbiotic algae. This algae is very important to the coral (see the text ‘Zooxanthellae’). The algae use photosynthesis and need light to do this.

So PAR then. This stands for Photosynthetically Active Radiation. In other words, light that is potentially useful to photosynthesis. It is measured in nanometers (nm).

In the sea, different colours of light are lost, some before others. The first to be lost is red, within a few feet of depth. Blue penetrates deeply, and is the only light left (except UV) after around 50ft. It is blue that is of interest to aquarists. It is stated that blue light of circa 420nm is of good use to zooxanthellae. Thus there are ‘actinic’ tubes and other tubes that are manufactured to peak at this point. Metal halide bulbs can be obtained with different spectrum outputs.

Blue is not the only colour useful to photosynthesis, but it has been found to be useful in a captive system. There are many corals that use this available light and they are usually lower in depth on the reef. There are corals close to the surface and obviously these receive much stronger light and more than just blue. The corals deal with this naturally, as there is much more light available for photosynthesis than is needed.

I reckon that is all that is needed. It really is a ’skim’ over the surface, as said lighting is a complex subject. As with so many things, one thing could be dependant on another, provided that yet another is present. I apologise to any lighting engineers who might see this text, but it is not intended for you.

Us aquarists need only understand what is needed and basically why on the different aspects of keeping a marine aquarium. In this case, it is the lighting that the zooxanthellae can use to photosynthesize, allowing our corals to prosper.

(Ref: Aquarium Corals. Eric H. Borneham)

---

Tags: aquarium, Aquarium Lighting, Equipment, marine-aquarium, saltwater-aquarium

Should You Run Your Protein Skimmer Full Time Or Part Time?

The protein skimmer assists in the removal of dissolved organic compounds (DOC’s) from the water column. The protein skimmers manufactured nowadays are normally exceptionally efficient - as long as they are kept clean!

So what do I mean by running your protein skimmer full time or part time?

Well basically a protein skimmer which is run full time is turned on 24 hours a day 7 days a week whereas a part time skimmer is on for less hours in the day - 12 for example.

So why would anyone consider this?

You have to look carefully at what you are keeping in your saltwater aquarium. If you are keeping fish only then I would recommend without hesitation that the protein skimmer be run fill time. Fish produce a lot of waste and we have to feed them so the protein skimmer assists in the removal of these items as well as others from the water.

If you keep a coral only or a mixed reef tank then perhaps it could be different. I say the word perhaps as you need to look very closely at what you keep in your aquarium. The reason for this is that we are interested in the load on the aquarium i.e. how much waste is being produced which the protein skimmer can then process. In a coral only aquarium then very little bioload should exist as corals put very little strain on the system. This does not mean that you do not need a protein skimmer as I personally would never have a saltwater aquarium without a protein skimmer installed.

In a mixed reef aquarium then you obviously have corals and fish, therefore like the fish only aquarium the fish are being fed, due to the feeding waste is produced which could easily impact water quality. Yet, how many fish are in the aquarium? How large are the fish?

What you can do is review your protein skimmer over a couple of weeks. Ensure that you have optimum water quality and then check your collection cup at the end of the period and see how much waste has been produced. If the cup is over half full then realistically you probably need to keep the protein skimmer running full time to ensure that everything is removed. If the cup is less than half full then faesibly you could potentially use a part time skimmer.

Of course this is not set in stone as each aquarium system is different. The decision ultimately comes down to you based upon your particular setup.

So why do it?

There is a lot of debate as to how much good is removed by a protein skimmer as well as bad. As protein skimmers have evolved over the years they have become more and more efficient. Due to this efficiency they can remove a huge amount from the water. This is great in one way as it assists us in both creating and maintaining the water quality which our aquarium inhabitants require however what else is removed?

Personally I have absolutely no idea. I am not a scientist and do not have the tools, skills or knowledge to be able to analyse the output from a protein skimmer and see what it contained. All I know is that it is brown and exceptionally stinky!

It is believed that some of the items potentially removed by the protein skimmer is used by corals as food. Corals receive the majority of their energy from the lighting which is provided to them, however they do receive a good amount from food captured in the water. This could be the likes of phytoplankton, zooplankton etc. Have you ever watched a documentary on the television about natural coral reefs? Have you seen how many particles are floating about in the water? Loads aren’t there - in the aquarium we do not have this amount as we have to use man-made devices in order to keep the water clean.

So potentially if you run the skimmer part time some of this life will not be removed and can be used by the corals as food.

There have been reports that when this is performed it has been noticed that the corals appear to have better colour and better polyp extension.

Another method is by actually feeding the corals yourself. You can purchase various ready made containers full of coral food which you feed to the aquarium. There are also various methods you can follow to make your own coral food. I will cover coral feeding in a future article.

Would I do it? - maybe but only if I was absolutely positive that it was not detrimental to water quality and I would be testing the water all the time.

Would I recommend the beginner do it? - Probably not - not just because they are new to the hobby but the aquarium is also new and needs to age a bit. Perhaps if only corals were being kept but even then I think that it should be run full time until the aquarists gains experience.

---

Tags: aquarium food, Aquarium Maintenance, Care, Corals, Equipment, marine reef, reef-tank

Give Me The Moonlight

Our marine aquariums for the most part, whether reef or fish only, are very natural, far more so than they were even just 10 years ago. Technology has advanced a great deal as well.

The lighting is designed to help the corals and also look reasonably natural, the filtration is varied but many, if not most, aquarists use live rock. Live rock is probably the best filtration available and there isn’t any more natural. With efficient - or perhaps a better word is imaginative - aquascaping, the aquarium now really can appear to be a ‘slice of the ocean.’

Most aquarists including myself sit and gaze at their aquarium and marvel at how lovely it is, and at the same time marvel at how livestock from a home such as the reef - connected to the huge volume of the seas and oceans - can possibly survive let alone thrive in a tiny aquarium. But they do.

There is a continuing search for better ways of using nature to improve things. One of these is the deep sand bed (DSB), another very natural way of filtering. The use of macro algae such as Caulerpa is another. There are more examples.

Trouble is, most aquarists have restraints, perhaps financial, or space available or both. I fall into the space category, though finances are not exactly without bounds.

There is one thing I have done to advance my system though. It isn’t unique, a lot of other aquarists have done the same. It doesn’t take up much space and certainly doesn’t cost a fortune, far from it. That last bit is perhaps a little unusual for this hobby!

I’ve given my reef moonlight. It’s very simple to do. This involves the use of LED’s (light emitting diodes). LED’s have been in the news recently as the technology slowly moves forward to challenge metal halides in the power lighting of a captive reef. In this case, that is moonlight, the LED’s have low output.

What I’ve done is obtain a set of four blue LED’s in a very small unit. This has been placed on the top bracing strut - out of the water - at one end of the aquarium. The lights are angled down to shine diagonally through the water. The power comes from the mains supply.

An extra electric timer has been placed in the cabinet below the aquarium. The moonlights do not come on in the ’dawn’ sequence, only at ’dusk.’ The sequence is marine whites off first, 15 minutes later the actinics turn off. 10 minutes before the actinics turn off, the moonlights come on, and stay on for one hour. Of course, the moonlights can be on for as long as the aquarist wants.

Unless an aquarist is experimenting with moonlight and corals, I am not aware of any real advantage to the livestock. The fish and shrimps seem to become accustomed to the main white and main blue lights going off in sequence, and ‘take to their beds’ just before the blues disappear (or mine do). The presence of the moonlights must make the sequence a little less abrupt however.

It is marvellous looking at the reef under full lighting and also just the main blue lighting, as they are both attractive. Under actinics some corals fluoresce and this looks terrific, and the blue colour picks out some coralline and similar.

In addition to the above main lights, if moonlights are used this extends the viewing period and offers a really quite magical scene. LED’s create a ripple effect, and flickering shafts of light shine diagonally through the water, picking up corals and other reef shapes.

So the advantage of moonlights is to the aquarist, offering more viewing pleasure. The icing on the cake is that the cost of these lights is low, the running cost very low, and the life expectancy of the LED’s very long. It cannot get better than that. So go on, indulge.

---

Tags: Aquarium Filtration, Aquarium Lighting, Aquarium Maintenance, Care, Equipment

Aquarium Lighting Advance

In years gone by aquarists lit their aquariums with tungsten lights. They probably had no idea of spectrum, probably had lots of algae growth, and I would imagine the heat output would have caused problems too. Methods advance.

Nowadays there are two main lighting systems, fluorescent tubes and metal halide bulbs. Fluorescent tubes are mainly used for fish only and soft coral systems, with metal halides lighting mostly hard coral reef systems.

Aquarists have a wide choice of tubes and bulbs, with spectrum being tailored to need. One major ‘fault’ is that to achieve high power output, that is, use metal halide bulbs, there is a premium to pay for electricity. In addition, nowadays we are more aware of our carbon footprint, with all the concern about global warming that has arisen.

Well, the ‘advance’ I’m writing about is not exactly new. I’ve written about it before at some length. The lights are LED’s, which up to now (as far as I am aware) have been available in two forms - moonlight low power and full lighting high power types. It is the high power types that have ‘advanced’.

Up to now the only LED lighting available to light a reef are full arrays, where a high number of LED’s are inbuilt, with different colours incorporated. These arrays come in different sizes for different size aquariums. Trouble is, they are very expensive despite the many advantages they offer (see under Articles and under the sub-heading Equipment - ‘LED Lighting’).

The advance is not so much in technology (as far as I know) but in choice. Power LED’s are coming on to the market which offer choice in much the same way as fluorescent tubes do.

The units which, as said, resemble a fluorescent tube, are a little under 20″ (circa 51cm) in length. They each have 5 LED bulbs and can be obtained as full spectrum, natural daylight, marine white, reef white, marine blue and reef blue. I am not aware at the moment what the difference is between ’marine’ and ’reef’ in the white and the blue. Perhaps one of the blues is the actinic equivalent?

Anyway, with LED’s the aquarist can now ’mix and match’ according to need.

The big drawback, as before, is cost. I understand the light ’tubes’ individually will cost around $175. Ouch! This is tempered however by the cost of running them, which could be as low as around $15 per annum. The lights run at 12v DC. The bulbs are said to last about 50000 hours! The heat output is reported to be very low, so further savings might be made on the cost of a chiller.

The only power output indication I’ve managed to discover is that at 50cm from the aquarium, the LED ’tube’ produces around 33% more light than a 24W compact fluorescent. Fluorescents are usually much closer to the water surface than that, but at a closer point the ratios would remain the same.

I’m hoping for more information particularly on power output. I don’t know if the lights will challenge the supremacy of metal halides yet, maybe the light output close to the water surface will be something like a lower powered metal halide positioned much higher? Hmm. Maybe?

The exciting point is that the LED is still developing and slowly presenting a bigger choice to the aquarist. If the LED now, or does eventually, offer flexible lighting fully suitable to the varied needs of aquarists particularly those with reefs, then metal halides, considering the running cost and heat output, will no longer dominate. Definitely so if the LED price falls somewhat.

I feel fairly certain that in the course of time LED’s will be the light of choice, particularly for reefs, with all the advantages, especially those of running cost and lack of heat into the aquarium. Power output is the thing for the reef - that will come if it isn‘t here already.

---

Tags: aquarium, Aquarium Lighting, Equipment, led lighting, metal-halide, saltwater-aquarium

Next Page »