Enough Light? Must Be

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)

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Ouch! Know Your Enemy

Last week I was helping my neighbour move a broken up concrete garage base to make way for a new one. Because the lumps of concrete were pretty rough I wore protective gloves.

Without warning a pain similar I suppose to having a red hot needle stuck into me occurred on the inner wrist. The pain didn’t last long, about a second, so it wasn’t severe. The only word I uttered was ‘Ouch!’ I saw the wasp leave, somehow or other it had got caught between my wrist and the glove. Over a couple of days my wrist did swell to an extent, but there wasn’t a problem though the itching was an annoyance.

When it happened I tried to recall the standard remedy. I knew that a wasp and bee had opposite sting make-up, one being alkaline and the other acid. Should I dose the sting spot with milk or vinegar? I wasn’t sure so I did both.

Later I found that a bee sting is acid, so milk would be appropriate, and a wasp sting is alkaline, so vinegar would be appropriate. Pretty straightforward really and seldom a real problem unless the person involved is likely to severely adversely react and/or is stung many times.

Australians often take a bottle of vinegar to the beach in case of stings. There are some nasty life forms that could make their presence felt. Another way if vinegar isn’t present is to use urine so I’m told (so perhaps those few beers on the beach could help in more ways than one!).

Vinegar, milk and urine are not the correct medications for all venomous stings and bites etc.

Marine aquariums are to be found in many places around the world. In the US and EU they are very numerous. Considering livestock, there’s a few that could cause problems.

In the sea there are some dangerous creatures and some of these find their way into aquariums. For example the blue ringed octopus is kept by a few aquarists. This little octopus, properly called Hapalochlaena maculosa, is around the size of a golf ball and is attractive, though the rings only turn blue when it is about to attack or as a warning to another life form considered too close. The size makes it a possibility for inclusion in a suitable aquarium. However, it has a deadly bite because it injects toxin.

Another dangerous creature is the stonefish (one type is Synaneichthyes verrucosus). I have seen a stonefish for sale, though only once, but why anyone would want to keep one I don’t know. The fish is sedentary, sitting still waiting for prey. They look very like a rock. On the back of the fish are 13 grooved spines which inject toxin if they penetrate the skin, somewhat like hypodermic needles. The intensity of pain and subsequent problems is subject to an extent on the number of spines that penetrated the skin. The pain is stated to be excruciating.
 
A problem caused by a blue ringed octopus or a stonefish needs immediate medical attention or death could occur. There are other dangerous creatures in addition to the two mentioned.

Most of us marine aquarists don’t keep such life forms. There are a similar few that are kept but are not as dangerous perhaps, but dangerous nonetheless.

One such fish, and well known, is the common lionfish, properly called Pterois volitans. There are other types but the common lionfish is the most readily available. The body markings are quite striking and the finnage beautiful. In the aquarium they need careful selection of companions or the companions could be eaten! The fins are the problem to the aquarist; they are able to inject venom that causes great pain.

Another well known and commonly kept fish is the foxface, properly called Lo vulpinus. These fish are also colourful and are a ‘different’ addition to the aquarium because of their head shape, though why they should be called foxface I don’t know. The danger with these fish again lies with the venomous fin spines which are capable of injecting venom which could take a long time to heal.

Another commonly kept life form is not a fish this time, but a coral. It’s very innocuous looking and kept in very many aquariums from beginner to advanced. It is quite tolerant and is usually able to resist some errors made by beginning aquarists. They are the zoanthids or button polyps which come in various polyp sizes and colours, normally covering the upper surfaces of a rock. Who would think there could be any danger from these? The danger comes from the species Palythoa, Protopalythoa and related species. Many aquarists handle zoanthids without any problem – in fact, problems from handling are rare. The fact is that the mucus of these zoanthids contains a neurotoxin which could be very dangerous or deadly to the aquarist. It is known that some tribes used to dip their spears in the mucus for use in battle and hunting*. So when one of these polyp groups is to be handled at the very least the aquarist should be sure there aren’t any cuts and abrasions on the skin. Wearing suitable gloves would be better.

The aquarium inhabitants mentioned above aren’t the only potential dangers that could appear. What is necessary is that the aquarist knows the potential problem(s) that could be introduced with newly purchased livestock to ensure he or she is happy with the situation. More important the knowledge should ensure the aquarist takes precautions and exercises caution when carrying out maintenance etc. The knowledge about livestock comes from some simple pre-purchase research.

In addition it is necessary, like a good scout, to be prepared. So as the potential problem is known the aquarist can find out from the internet or other sources what course of action should be taken should a mishap occur. Obviously medical assistance could be required, but it is important to be able to take initial action, if any, to help control the problem before medical help is available. It is also important to be able to advise the medics what it is that has happened, for example a puncture from X fish that is known to carry venom. At the extreme it could save your life.

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Breeding Seahorses

Despite the fact that more advanced marine aquarists visit Aquaristsonline in increasing numbers the website was originally targeted at beginners. Nothing has changed, so why is anything being written about breeding which is in the area of the more advanced among us?

The answer is that earlier, and also more recently information has been given about keeping seahorses, such as how to create the necessary species aquarium etc (see blog and ‘Articles’). I have a soft spot for these endearing creatures and at the same time am well aware of the pressure on them in the wild because of collection. Therefore it seems reasonable to ‘round off’ with something about breeding.

In the first place it must be stated that breeding these creatures is not for the complete beginner. Any aquarist who has bred marine fish including the ‘easier’ clowns could proceed. Don’t let that put you off though; it’s not beyond the scope of anyone who has accumulated some experience. How can the level of experience be judged? The aquarist must be absolutely capable of maintaining continuous high quality seawater, and this is easily shown after say a year with the use of test kits. Definitely zero ammonia and nitrite, and a very low level, if any, of nitrate. Phosphate is best undetectable. Finally, any other requirements specific to the type of aquarium system need to be acceptably stable at the correct levels, such as calcium etc. If the aquarist is able to maintain the required parameters as a matter of course then ok, the seawater in the seahorse aquarium will also be maintained at high quality. It is clear that seahorses, as with fish, need to be happy and healthy before there is any chance of breeding, and this depends very much on their environment.

Now I’m not going to start advising the best way to breed seahorses and how to do it, there are those better qualified than me. So what I have done is provide two links:

http://www.petplace.com/fish/how-to-breed-a-seahorse/page1.aspx
http://www.spc.int/coastfish/News/LRF/5/10Breed.htm

Successfully keeping a seahorse aquarium is very satisfying. Actually breeding them must really be wonderful and a source of great pride. In addition, the local fish shop or marine aquarist colleagues would no doubt be interested in the offspring so there won’t be any difficulty in sourcing placements. Finally of course the pressure from collection will be eased that little bit more.

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Making Live Rock

The major bio-filtration media in use by marine aquarists, whether they keep a reef or fish only system, is probably live rock and for good reason.

Premium live rock is rock that has been fairly recently harvested from around the reefs, meaning it is ‘rubble’ rather than hewed from the reef itself. This rock has growths of all sorts which could be of interest to the aquarist. Unfortunately, live rock needs to be cured after import which simply means that all the dead and dying organisms on and in the rock have to be removed, meaning that pollution will not occur in the aquarium. However, for the most part there are tougher organisms that do survive and they could make an appearance in the aquarium, this appearance could be months after the rock has been introduced. Live rock can also harbor unwelcome organisms, such as the aquarium weed aiptasia, an anemone that could become a real nuisance without controlling attention.

In addition to natural organism introductions with the rock, it is very decorative. Reef and fish only aquarists are able to construct a very interesting and decorative structure which suits livestock very well.

The next great attribute of live rock is mentioned in the first paragraph – bio-filtration. Living organisms in the aquarium will literally be poisoned unless there is some means of negating the toxic substances that they produce. The two major toxins are ammonia and nitrite, and a much less dangerous one is nitrate. Dwelling on and in the live rock are oxygen requiring bacteria which convert the toxin ammonia to the toxin nitrite, which is then converted to nitrate. Bacteria living within the rock also require oxygen but find it hard to obtain, therefore they extract it from the nitrate which breaks the nitrate down releasing the residue from the aquarium as gas. The process from ammonia to gas release is known as the nitrogen cycle.

Live rock is a great commodity for the aquarist, providing the major and essential job of bio-filtration and also doubling up as decoration. The rock must of course be present in sufficient quantity to deal with the bio-load present, which is created mainly by fish.

There’s only one problem and that is cost, it’s expensive, particularly the premium grade. It’s expensive to air freight rock. This cost could be controlled up to a point by using base rock as the lower part of the rock structure and premium grade for the surface – but it is still expensive.

One way of avoiding this cost is to create live rock, which isn’t difficult. What is required is inert porous rock, that is, rock that is known to be free of any substance that could be harmful in seawater and also porous. This type of rock is often available in local fish shops and at a very much lower cost than the live variety. It isn’t any use purchasing solid non-porous rock. The second requirement is that there needs to be as much rock as would be used if the live variety were bought, which should ensure that the amount of bio-filtration media will be adequate.

If necessary the rock is thoroughly rinsed before it is placed in the aquarium to form a structure as required. The aquarium is then filled with seawater (note the net gallonage for future use) at the required specific gravity (SG) and heated to the design temperature. Seawater circulation should also be turned on. At this stage there isn’t any need for lighting. The seawater should be left to settle down to the required parameters. Check the seawater SG once it has heated up as temperature could affect it.

Once the seawater is at the required SG and temperature attention can be given to processing the rock. Anyone who has ever used a canister filter for bio-filtration will be aware of the process. A commercial maturation fluid is obtained and added to the seawater at the amounts given in the instructions. Test kits for ammonia and nitrite are also required, and the seawater should be tested in accordance with the instructions. Eventually the ammonia reading will disappear, followed by the nitrite reading. Once the aquarist is sure the reading remains at zero for both, the rock can be considered to be initially mature, that is, there is an initial population of bacteria to deal with toxins.

A test should now be done for nitrate; a level will probably be clearly seen. This nitrate should be reduced by a seawater change until it is as low as possible or preferably undetectable.

Slow stocking can now commence, turning the lighting system on of course. It is important that ammonia and nitrite tests continue, if there is any indication of either ammonia or nitrite stocking should cease until the reading(s) are zero again and remain so. The bacteria need to adapt to the increasing bio-load and must be allowed the time to do so.

Eventually of course the aquarium will be stocked as required. The bacteria population is able to stabilize and after a further say three months can be considered as fully mature. Routine seawater changes, as with any system, need to continue as does testing.

Wait a minute though; we’re supposed to be creating live rock which should be able within reason to deal with nitrate. So it will, in time. It takes longer for the nitrate reducing bacteria population to establish, and once it has the nitrate should be controlled. Relative to live rock and nitrate what does ‘within reason’ mean? It simply means that if the aquarium is often overfed and the toxin reducing bacteria produce a lot of nitrate, and the aquarist is missing routine seawater changes, the nitrate could be too high for the bacteria to control.

Ok, so now we have an aquarium filtered by live rock. What about the natural growths that could occur (though not always) with natural live rock? These will obviously be absent as the rock was initially dead. With both the fish only and reef system, if the environment is of high quality it shouldn’t be long before encrusting algae’s make an appearance. In a fish only system it could be necessary to seed with a small piece of rock from a friend’s aquarium that already has encrusting algae on it. In a reef system, when the aquarist introduces corals they will usually be attached to pieces of natural rock. These rocks should contain organisms that should seed the other rocks provided a high quality environment is maintained. Before long the previously dead rocks should look completely different – just like natural live rock.

So for a considerably reduced price live rock is achievable. What the aquarist needs to provide is some patience (required by all marine aquarists) and considerably less money. There is great concern about the future of the wild reefs and concern has been expressed about the impact of live rock collection, so the aquarist who produces his/her own will be assisting with reef protection.

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Remember The Lighting

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.

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Interesting Maybe, But It Doesn’t Matter

Interesting?

O3        +  NO2 ………> O2         + NO3
(Ozone + Nitrite ………> Oxygen + Nitrate)

Could be, but in the majority of cases the answer is no.

A potential marine aquarist or even an existing one keeping a reef or fish only system is likely to shy away from anything approaching scientific, and fair enough. (The above is straightforward and understandable if the symbols are understood but gives the general idea). Being a marine aquarist doesn’t mean a white laboratory coat is required or a ‘professor’ appearance, though there are one or two aquarists who love to mystify the marine aquarium and elevate their accomplishments. There isn’t any need to boost success with an aquarium; it is there for all to see.

Some books contain explanatory formulas that would cause consternation with any ordinary person. This isn’t to say that scientific formulas are a waste of space, they aren’t. They are of use to a scientist of course, and interesting to those with experience who wish to delve deep. The same principle applies to many hobbies.

The hobby needs science; it is the scientists who explain. The hobbyist doesn’t need to be involved at that level.

Even when avoiding science troubles still arise. The new aquarist, particularly if interested in a reef system, is still faced with gobble-de-gook. There seems to be an unending stream of needs that must be met or failure will occur. Worse, much of this is in shortened version such as KH (for Kelvin), SG (for Specific Gravity), Alk (for alkalinity), temp (for temperature), calc (for calcium), ppm (for parts per million) etc, never mind the variations with lighting; there isn’t a need to go on. Much of this shortened terminology is often used when hobbyists are ‘chatting’ on forums.

Even when the potential aquarist knows what it all means, the problem doesn’t stop. Seawater quality is the number one requirement so the beginner starts to delve into that. The important parameters are discovered but then there are comments on forums and in books about balance – if this is low that will suffer, generating more confusion.

The beginner can flounder at this stage and start to wonder if it’s worth it, it’s supposed to be an enjoyable hobby, at least that is what was understood at the beginning.

The beginner is going to be a successful marine aquarist with some perseverance and if research is done. The research doesn’t need to be into how everything works and what depends on what. The marine hobby has been going for long enough for scientists and advanced hobbyists to have discovered what leads to success. This doesn’t include deep studies into seawater make-up as an example.

It is now well known what ‘high quality’ seawater means. There are tables available that suggest the levels of various items. For example specific gravity is usually quoted as 1.022 to 1.025 for a fish only system, and 1.024 or 1.025 for a reef system. So the aquarist maintains the seawater at the chosen level having considered the given advantages of numbers within the scale. Other parameters are maintained at the levels suggested for them and doing so generally removes the problem of imbalance. It is also known what is not required in the seawater, for example nitrate. Again there are guidelines that suggest upper limits for different systems, so these levels can again be maintained. The beginner aquarist will also have learned of the need for stability and how to achieve this.

So the marine hobby isn’t a scientific challenge for a beginner or anyone else. All that needs to be known are the suggested levels for a marine system, and then maintain them. It should also be said that the system itself needs to be basically adequate, but again these needs are well known and obtainable.

So the mystique is gone. It must be said that patience and a basic understanding are required. The basic understanding is just that, the numbers that represent the levels that livestock require within an adequate system. When this is achieved and maintained, all things being equal success is on the way.

That doesn’t mean to say however that the aquarist never delves into the world of science. Once the ‘bug’ has bitten, some aquarists have to pursue knowledge about ‘why’, and that is to the advantage of us all.

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How Did I Know The Rock Had Become Live?

All marine aquarists are aware of live rock. It’s the stuff that perhaps the majority use for bio- filtration and it’s also excellent as décor, be it a reef or a fish only system.

Good mature live rock has the usual bacteria present, those that convert the toxins ammonia and nitrite to the much safer nitrate. Unlike a canister filter where the nitrogen cycle stops after the production of nitrate, live rock within reason will deal with nitrate. This is because the bacteria that dwell deep inside the rock would also prefer to use oxygen directly, but because it is in very short supply they remove oxygen from nitrate which breaks it down.

When I set up my current soft coral reef system I used two canister filters for the bio-filtration. (The photo shows the reef in part. You can tell I took the photo!) The bio- media was Eheim sintered glass. It worked very well. Being aware that nitrate could become excessive I built a denitrator based on suphur and this ran from when nitrate was noted as being present even though the reading was very low. Better to defeat a potential problem than wait to tackle a real one. Once the denitrator was matured the nitrate disappeared and I never had any readings at all. This was over the first 5½ years of the aquarium’s life. It has to be said that the fish load is very low; there are two small fish (a blue damsel and a flame angel) in 43 gallons net of seawater.

The reef is built of what is named ‘grotto rock’. This doesn’t come from any grotto so why the name I don’t know, however it’s ideal for marine use as it is totally inert and full of crevices and holes. Just as important, it’s very porous. The rock comes in all sorts of shapes and sizes and it was great fun creating the reef.

The reef developed over the years and I noted the lack of nitrates. I thought I’d do a little experiment at one point to prove the effectiveness of the denitrator; this experiment consisted of turning if off. Difficult!

I monitored the nitrate level and found that all readings were zero (I suppose I ought to state that nitrate was undetectable with the test kit). I left the denitrator off for a week, two weeks, which turned into months. Still nitrate didn’t appear. The canister filters continued to run so nitrate would be produced.

I like looking at the reef from various points in addition to the front and sides. This often involves lying on the floor and peering into the aquarium. This sometimes occurs at night when most of the little beasties are about. The rocks I thought looked more like live rock than the real stuff, with all the worm growths, algae etc. I then wondered if it was in fact live. This thought was supported by the lack of nitrate, the canisters were producing it and perhaps bacteria were removing it? I realized that I did routine seawater changes and this would tend to reduce nitrate levels as well.

The rocks were now live, why not? It was an excellent home for bacteria after all. However, at the end of the day a rock looks like a rock, there’s no way a bacteria presence can be checked. It is a known fact that bacteria exist on surfaces within the aquarium in addition to any intended bio-filtration area, but would there be sufficient to support the aquarium completely? Surely the canister filters would be taking the majority of the bio-load?

I have two canister filters running as said, so it was easy to check. At the next scheduled clean of one of the canisters I removed the bio-media and ran the canister empty (seawater is returned to the surface for oxygenation and to agitate the surface). A careful watch was kept and there weren’t any unwanted effects.

So far so good, but the next stage was a little more cautious. Even though the bio-media from the first canister had gone, maybe the second canister was handling everything, so with the second canister, when the time was chosen to remove some bio-filtration media I only removed half of that present. Hopefully that left would prevent any major disaster from occurring. The amount left was one quarter of the total original amount. This was left for a month with everything being carefully watched. No problems.

Now came the crunch – remove the final bio-media. This was done and both canisters now ran empty. Feeding and maintenance continued as though nothing had changed. Nothing untoward happened.

The system continues to run normally and it is now approaching its 7th year. The inert rock is now live.

To be honest I wasn’t really surprised, though it was very sound to use caution. One way of producing live rock is to mix inert rock in with live; the higher the live proportion the quicker the inert variety converts (it still takes quite some time). There wasn’t any live rock in the system at all at the start; it was all inert, so how did it convert?

The first possibility is that ‘overspill’ from the canisters occurred though perhaps this is unlikely, I don’t know. The second is that bacteria developed on and in the rocks naturally and these expanded in number.

To my mind the most likely explanation is that the bacteria were introduced, though some could have appeared naturally as suggested above. Most of the corals that were introduced are attached to rocks and of course they were attached to these when collected – these rocks are live. So the inert rocks were colonized by the bacteria from the live coral rocks.

When the bio-media was slowly removed from the canisters the bacteria on and in the rocks would have expanded to deal with the increased load and, hey presto, the system is now based on live rock.

The denitrator sulphur media has been cleaned and is not in use. I haven’t actually removed the unit as it isn’t in the way. The good thing is there isn’t any more need for it to be maintained though the maintenance wasn’t a problem. The worst part was the flow, denitrators have a very slow flow and this was occasionally problematical and a bit of a headache. No more of that though.

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