You Need To Have Enough Filtration In Your Aquarium

A successful marine aquarium is a wonderful sight. It doesn’t matter whether it is a fish only, coral only, or fish and coral system, there are certain items that need to be up to the job.

The first essential requirement is seawater quality, closely followed - at least in a coral only or coral and fish aquarium - by lighting. It is the need for seawater quality that makes filtration so important.

There are basically two types of aquarium filtration, excluding protein skimming which is often counted as such. The first is mechanical/chemical filtration and the second biological.

Mechanical filtration is where media removes sediment from the seawater by trapping it in suitable media. This is often done by using a canister filter which needs to be cleaned regularly and the media changed if it is showing signs of wear or failure. Mechanical filtration is not an absolute requirement and many aquarists do not use it. It is usually only necessary when there is a fair amount of sediment floating around in the seawater. Before employing a mechanical filter, it is best for the aquarist to ascertain why there is sediment and try to correct the problem.

Chemical filtration is also often done by using a canister filter and can be in conjunction with a mechanical stage - if so the mechanical stage normally comes first. Chemical filtration covers activated carbon, phosphate removing media etc. Again it is not mandatory to use this type of filtration, though some aquarists use activated carbon to supplement the protein skimmer and others run an anti-phosphate media continuously (phosphate is a nuisance algae nutrient and is mainly introduced with food).

By far the most important filtration is biological, and this applies to any type of system. The filtration carries out the ‘Nitrogen Cycle’, which is something all aquarists should clearly understand. Livestock introduce a toxin into the seawater, namely ammonia. This toxin is deadly to life forms in low concentrations but fortunately Nature has the solution. The biological media provides a home for bacteria in their millions, and the first group of bacteria convert the toxic ammonia into nitrite. Unfortunately nitrite is also a toxin and very nearly as bad as ammonia. However, a second group of bacteria convert the nitrite into nitrate, which, though problematical in a high enough concentration, is not generally harmful. If the Nitrogen Cycle is able to run the full course the nitrate is converted to gas which escapes the seawater.

There are one or two points that need to be remembered about the bacteria that provide this essential service. The first is that the bacteria that convert ammonia and nitrite are oxygen hungry, and to ensure their proper function it is necessary to provide seawater rich in oxygen by having adequate seawater circulation and air/water interfaces.

The bacteria that are able to convert nitrate to gas are not the same. They would use oxygen if it was available, but if it is not they take the required oxygen from the nitrate, thus breaking it down. Therefore the bacteria need to be in a very low or no oxygen environment to ensure that the required function is performed.

If for example a canister filter is being used for biological filtration the media is constantly exposed to oxygen. Therefore the breakdown of ammonia and nitrite will occur but nitrate conversion will not. Nitrate will remain in the seawater and will increase unless other adequate measures are taken.

If the biological filtration is by good quality live rock, then the full Nitrogen Cycle, that is ammonia-nitrite-nitrate-gas, should occur. This is because the oxygen loving bacteria accumulate near to the surfaces of the rock, and the bacterial nitrate converters are deep inside where oxygen is depleted.

Having considered all of this, it is clear that there needs to be adequate filtration material to accomplish the biological task. For example, a fish only system can employ live rock. Fish are producers of ammonia, much more so than corals, and an adequate amount of good quality live rock is needed to process the toxins. The live rock amount would need to be increased if the fish numbers were high as obviously there would be more toxins produced. As a general guideline 1½lbs of good live rock is considered necessary for each gallon in the complete system. So if there is a sump, count that in. There is a problem with the ‘weight system’ as live rock can be of differing weights, therefore when purchasing seek advice.

Similarly, when using a canister filter (or similar) for bio-filtration it is important to ensure two things - first that the canister can contain sufficient bio-media for the intended load and second that the flow rate through the filter is adequate. Manufacturers will advise the recommended aquarium size for canister filters, and media manufacturers will advise the suggested bio-loads.

Mechanical/chemical filtration is not so essential, so reading the media manufacturer’s recommendations is sufficient, if these types of filtration are required at all.

Stocking a marine aquarium without an adequate amount of bio-filtration will soon become obvious to the aquarist - sickly livestock and quite likely losses. Inadequate bio-filtration is likely to hit fish systems the most as they produce most toxin with their life functions. However, all systems require adequate bio-filtration, Nature’s free and essential service.

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Tags: Aquarium Filter, Aquarium Filtration, Aquarium Lighting, Care, Equipment, Water Quality

First Introduction - Fish Or Invertebrate

The majority of aquarists decide that the first introduction to their aquariums should be a fish yet does it need to be this way.

I fully understand why this happens and perhaps this is due to historic reasons where aquarists used hardy fish to assist in the cycling of their aquariums. Something which I am glad to say is not done anymore. Perhaps it is the movement and colour of the fish which draws the eye. There are many reasons as to why people choose a fish as the first inhabitant of their aquarium. It uis of course not up to me to sway their decision in any way but perhaps people believe that a fish has to be the first introduction.

On another note if the aquarium is a fish only aquarium then the aquarists will of course be introducing a fish first!

For the aquarist with a reef aquarium however there is another choice especially when live rock is used as the filtration but it does not matter what filtration is employed. Live rock even when matured correctly is not very sterile and therefore may carry opportunistic parasites. When a fish is caught in the dealers it is put under immense stress due to the catching, the bagging, the transport etc. When the fish is introduced to the aquarium its immune system may be lower than normal and in a reef tank filtered via live rock it may become prey to opportunistic parasites.

I appreciate that the above can happen at any time in the aquariums life however at the very start the aquarist is learning and if a fish is lost at the very start then this is sad for obvious reasons however the aquarist’s confidence in the aquarium and his/her own abilities and may give up the hobby.
There are certain fish which are more resilient than others however a lot of these fish - damselfish for example can become problematic later due to the aggressive nature and it is very hard to remove a fish from an aquarium with live rock in it!

Another method at the very start instead of fish is introducing hardy invertebrates.

By introducing hardy invertebrates first the aquarist will gain experience in acclimatisation techniques as well as stocking techniques. At the very start when the aquarist’s knowledge is low for want of a better word it is probably fair to say that a fair amount of tinkering will be employed. What I mean by this is that the aquarists hands will be in the aquarium a lot moving various corals around as well as the relevant water movement devices until they are satisfied that the conditions provided in the aquarium are suitable for the aquarium inhabitants.

If the decision is made to introduce invertebrates prior to fish then the aquarium, as with fish must be ready for the introduction of them. By this I mean that the nitrogen cycle has completed, there are no large algae outbreaks evident or they are under control and the water conditions are maintained in accordance with the recommended levels. For examples nitrates should be low as should phosphate levels. More than that the water conditions should not just be maintained they should be stable.

With the aquarist deciding to introduce invertebrates in the first instance the equipment purchased and installed should be capable of support the life in the aquarium. For example the lighting needs to be correct. This may sound basic but I hear of a lot of people trying to keep corals under lighting which to be honest is just not suitable for them.

At this point - actually a lot earlier the aquarist should know what corals, fish etc that they want to keep and should have based their purchases around this decision. At this point in the aquariums life you would not be looking at introducing an SPS coral like acropora etc as the aquarium is simply not ready for it.

At this point the corals you will be interested in purchasing are the ones which are not too expensive and do not have the colour of the majority of SPS corals. This is not to say that these corals are dull and colourless as they are far from it but when you compare prices you will see what I mean!

Speaking of purchase again I recommend that you build a relationship with a local dealer, another hobbyist or an online area (like Aquarists Online hint hint…) where you can go and ask advice as to what is suitable etc. Building a relationship with others is important as you can use their experience, their knowledge to your advantage o=plus you can learn a lot about the hobby and will hopefully not make expensive mistakes.

When selecting corals you are looking for corals which are suitable for the beginner. When looking you will probably see some exceptionally colourful species. I would probably stay away from these as there are some species which do not contain zooanthellae and require feeding for them to thrive. A good example of this is the sun coral. There are also other colourful ones which are probably for more advanced aquarists or aquarists who have had stable aquariums for a long period of time.

You have to remember that the aquarium is new and the water, rockwork, sand, glass, equipment etc all needs to age. You can always come back to these more colourful corals when your confidence has grown by maintaining a reef aquarium for a number of years.

In my opinion the list below details what I believe to be good ‘starter corals’ and are suitable for first introduction.

• Button Polyps
• Xenia
• Mushrooms
• Leather Corals
• Star Polyps

This does not mean that you should not introduce fish. I personally think that an aquarium with just corals in and no fish lacks movement however I think that perhaps more aquarists should introduce invertebrates prior to introducing fish to gain both confidence in themselves as well as giving the aquarium time to settle.

This of course also does not mean that you will not get problems when introducing fish at a later stage. You might but just remember to acclimatise them properly and use a quarantine tank.

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Tags: Aquarium Filter, Care, Equipment, invertebrate, live-rock, nitrogen cycle

How Fast Should You Stock The Aquarium

Throughout the years lots has been written about the stocking rates in saltwater aquariums - some of this information has been very informative and unfortunately some has been very misleading.

Misleading information provided has been along the lines of ‘1 cm of fish for every 5 litres of water’, ‘1 cm of fish for every 13 litres of water’ etc.

As you can see just from the above two examples it can be very misleading!

On top of the above there has been limited differentiation between fish only aquariums, coral only aquariums and mixed reef aquariums!

The main trouble is when it comes to stocking the aquarium - each aquarium is different. Each aquarium has different equipment, different animals etc. Even if you have two aquariums with exactly the same equipment then they would still be variances.

Overstocking in an aquarium is unfortunately something that the majority of aquarists do. For a long time they get away with it until something changes and the aquarium starts to go downhill. Basically if the correct care and maintenance is performed on a weekly basis and no equipment fails then some aquarists may be able to get away with overstock - until some area of the care and maintenance is missed, a piece of equipment fails and then the trouble starts.

The issue is not just with the aquarium being overstocked. Another issue is when the aquarium is stocked too quickly. This could either be that fish are introduced into the aquarium prior to the aquarium finishing its cycle, too many fish are introduced at the same time or not enough time is left in between the introduction of fish.

The first thing that the aquarist needs to ensure is that the aquarium is ready for the introduction of fish. By this I mean that the filtration in the aquarium is ready to process the waste created by the fish, uneaten food etc. This, as already mentioned is the cycle. In the cycle Ammonia is converted to Nitrite which is in turn converted to Nitrate. Both Ammonia and Nitrite are toxic to fish therefore no readings of these should be evident in the system.

At first testing only for ammonia will suffice, then testing for nitrite. When the ammonia levels reduce the nitrite should increase which should then reduce only for the nitrate to increase.

Nitrate is not toxic to fish but should be controlled either by water changes, natural methods etc to ensure that it stays within the recommended parameters for the type of aquarium you keep.

Once you have no readings at all for ammonia or nitrite then the aquarium is ready for the introduction of a fish - just the one don’t get greedy and overdo it. I appreciate that this is hard as there will be lots of beautiful fish in the shop which you could walk out with but you need to resist the temptation.

Before you go out to the shop though you need to realistically have a think about what fish you are hoping to keep in the aquarium (as well as corals and invertebrates if you are hoping to keep these). When you are thinking about this consider talking to more experienced aquarists or a couple of aquarium shops who you have started to build a bit of trust with. In my opinion it is good to build a good relationship with your local fish shop as they will get to know both yourself and your aquarium and you never know when you may need them.

When thinking about your list what you want to ensure is that all the fish you hope to keep will live happily with each other (and corals/invertebrates if you are keeping them).

There is something else you need to think about at this point - the hardiness of the first fish.

It is recommended that a hardy fish be introduced first into the aquarium at the start of its life. In my opinion this is correct as everything in the aquarium is new and basically the water is raw and too clean. A hardy fish is good but what you do not want is a territorial fish. A good example of this is the damsel fish. Whilst the fish is hardy it will quickly believe that the entire aquarium is its territory and when you introduce other fish into the aquarium they could easily get bullied which in turn leads to stress, disease and possibly death.

What you are looking for is a fish which is hardy yet is not territorial.

A good example of this is the common clownfish - tank bred if possible.

So let’s pretend at this point that you have gone to your local fish shop and ignored all the other fantastic fish and purchased just the one - a common clownfish.

Well done to you!

Now you have it home and you need to follow the correct acclimatisation procedures. A lot of people ask me if they need to quarantine their first fish. In my opinion there is no need to do this as there is nothing else in the aquarium which could be effected if this one becomes sick but if you are on the cautious side then quarantine the fish for a week - it won’t do any harm.

One the fish has been acclimatised to your aquarium it should soon start to explore, take food and perhaps even become bold.

At this point you may become tempted to go out and purchase one, two, three etc more fish. You should not do that though. You need to test the water. Prior to adding the first fish to the aquarium the filtration had nothing to deal with other than the cycle and any areas of die off which may have occurred. Now that a fish is in the aquarium you will be feeding it and not all that will be eaten and will fall to the bottom. What is eaten will eventually pass out of the other end and needs to be dealt with.

All this is processed by the filtration and the filtration needs time for the bacteria levels to increase. This is what you are waiting for - stability in the filtration.

This can again be done by testing for nitrite and nitrate. Even if these readings are zero for nitrite I would still wait a couple of weeks prior to adding a new fish. Give the aquarium time to settle and enjoy your new fish.

Once your readings are ok and at least a couple of weeks have passed then you can go and get another fish if you want to. Basically at this point you do the same again. Test the water and wait for stability.

Basically you should stock the aquarium very slowly. The quicker you stock it the more load you are putting on the filtration system and it may not cope. That in turn will mean that you may get ammonia or nitrite readings which are not good and as said are toxic to fish.

Also don’t forget that the faster you stock the aquarium the quicker it will get full. Enjoy stocking it and take your time.

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Tags: Aquarium Filter, Aquarium Maintenance, aquarium-livestock, Care, Equipment, quarantine

Can Decorative Sand Be Used For Filtration

This is a very good question which I was asked recently via email and I thought that I would detail it here for others to read and hopefully benefit from.

A lot of aquarists decide to put a small amount of decorative sand in the bottom of the aquarium to make it look more natural. This sand is normally something like coral sand, live sand etc.

Normally a small scattering is put in the aquarium - just enough to cover the bottom of the aquarium. At first the aquarium does look very natural however before long the sand starts to get clogged up with detritus, uneaten food and unless the aquarist cleans it then it can start to look very dirty.

Whilst looking into possible methods to keep it clean the aquarist may stumble upon a term called deep sand beds. After a small amount of research the aquarist may decide to ‘give it a go’ and after purchasing more of the sand installs it into the aquarium and believes that he/she now has a deep sand bed.

Wrong I am afraid and this is a deep sand bed which is probably destined to fail.

The reason for this is that the sand used in a deep sand bed has to have sand particles which are within a given size range. This is so that the animals which live in the sand are able to move the sand around. This is a term which is called turning the sand bed over. The animals will not magically appear. Some will migrate from the live rock if this is used in the aquarium, however the majority will need to be introduced by the aquarist. Not just once either the bed will need to be topped up from time to time. Once the bed has animals in there they then need feeding so that they can reproduce and increase the diversity in the sand bed. For this they need to be fed by placing some food directly onto the sand bed alternating where the food is placed. Other animals can also be purchased and introduced to the aquarium to assist in the cleaning up of the sand bed. These can be hermits, starfish etc but they have to be ones which will survive in a sand bed.

The other thing that is required is the actual depth of the sand bed. The sand bed needs to be a minimum of four inches in depth. Having a deep sand bed of at least this depth will create a bed which is low in oxygen at the bottom. When this happens this allows for the relevant bacteria to live which will assist in the filtration.

There are a large amount of aquarium stores now that sell sand which is designed for use in the the creation of a deep sand bed. There is a variety of colours to choose from however personally I prefer the natural ’sand’ looking colour!

A deep sand bed is a very powerful tool for filtration and is often underestimated. Combine a deep sand bed with live rock and you have an aquarium filtration system with a large amount of power. As long as it is properly setup and properly cared for.

In answer to the question - yes decorative sand can be used for filtration as long as the fundamentals of deep sand beds are understood.

Below are links to two articles we recently wrote on this subject:

The Deep Sand Bed - One Of The Most Effective Filtration Methods

Deep Sand Bed Construction

Feeding a Deep Sand Bed

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Tags: Aquarium Filter, Aquarium Filtration, deep-sand-bed, live-rock, plenum, Water Quality

The Plenum - Could It Work For You

The word plenum is not a term which the majority of beginners have actually heard of especially when it comes to filtering the aquarium. The plenum however is very similar to that of a deep sand bed however both the creation and design are entirely different.

So what actually is a plenum?

A plenum is not a filtration unit but is actually a space which is located under the substrate and separates the substrate from the bottom of the aquarium.

This space (the plenum) is full of both the water and any organic waste as the water is diffused into it. A plenum is also sometimes referred to as a Jaubert system as Dr Jean Jaubert was the individual who discovered it.

The structure of a plenum is actually very very simple. It is basically a deep layer of substrate which is suspended above the bottom of the aquarium to create a space or a void if you will.

How it works is, although slightly scientific, also relatively simple.

As the water moves slowly through the substrate the nitrifying bacteria in the upper level use up all of the oxygen in the water and convert the ammonia to nitrite and then the nitrite to nitrate. The nitrate which remains is the transported with the water down towards the plenum. As the water reaches the lower levels of the substrate the nitrate is then slowly broken down into nitrogen gas by the denitrifying bacteria which live in the very low oxygen levels of the substrate.

The reason the water moves slowly through the sand is due to the anaerobic action being performed in the lower levels. The anaerobic actions produces heat which heats up the water in the plenum area. This heated water moves up through the substrate which therefore displaces the cooler water above it causing the water to move through the substrate at a very slow rate.

A slow rate of water movement is important in a plenum as it assists in the prevention of a dangerous build up of hydrogen sulphide.

The upper levels in the substrate will become home to various organisms which can either be introduced via the aquarist or are organisms which have relocated from their home in the live rock. These are very important, the same as they are in a deep sand bed. Their job is to keep the upper levels of substrate ‘turned over’ and clean from both detritus and waste.

The above is how a plenum operates but how do you actually make one.

Again this is relatively simple. Not as simple as a deep sand bed as it does require a bit of DIY but simple all the same.

The items listed below are required to make the plenum. This list is not set in stone and can be modified to suit your/the aquariums needs.

Marine safe PVC piping.
Egg crate to make the grid from.
Screening.
Aragonite based sand with a granular size between 1 and 2 mm.
Live Sand.
Silicone.
Tie Wraps.

The recommended minimum required depth of substrate in a plenum is 2 ½ inches when placed on top of the plenum grid therefore you need to ensure that you obtain enough aragonite/live sand to accomplish this.

The first thing you will need to do is actually create the support which the substrate which sit on top of and create the plenum. Personally I find that marine safe PVC pipe is the best for this. These, when laid on their side provide a lot of strength for the substrate held above it.

I would recommend that you cut this piping in lengths of two inches or so and ensure that you have enough of them to support the weight of the substrate above it. Remember that you may also be placing rock on top of the substrate in the aquarium so make enough of them to support this as well. If you are unsure make more than you think you will need.

Once all the support have been kit you will now need to make the grid. The grid is basically there to hold the substrate up and also to prevent any of the substrate from falling down into the plenum area and effectively making it useless.

The easiest way I have found to do this is use eggcrate and cut this to the same dimensions as the inner dimensions of your aquarium. It does need to be noted that the grid needs to be a very tight fit so take your time cutting it. Once cut it can then be attached to the supports. I have found that tie wraps are excellent for this.

The basic structure of the plenum is not in place, however if the substrate was to be placed into the aquarium at this point it would simply fall through the eggcrate into the void. This is where the screen is used.

Cut the screen so that it is slightly larger than the inner dimensions of your aquarium. Once cut carefully place it into the aquarium, fold up the edges and carefully silicone it to the side of the aquarium. You will need to allow the silicone to cure which normally takes about 24 hours but once cured you should have a screen which no substrate will fall through.

Once cured you will be in a position to add the lower level of substrate. Add 1 ½ inches or so of aragonite and give it a really good stir using your finger to remove as many pockets of air as possible. Also be exceptionally careful not to tear the screen otherwise all your hard work will go to waste.

Now that the first layer is in place you will need to cut a second screen to slightly larger than the inner dimension of the tank, and silicone it in place as you did the first screen.

Once the curing process is complete put another 1 ½ inches of the aragonite sand into the aquarium. As with the first layer give it a really good stir with your fingers to remove as many air pockets as possible again being careful not to damage the screen.

Now we are ready for the live sand. Add about 1 inch or so of live sand to the top of the final layer - a screen is not required this time as it does not matter if the live sand mixes with the top layer.

The plenum is now complete and ready for water. When filling with water fill it slowly to avoid creating any air bubbles and mixing all the sand up.

So now we should have a plenum area at the bottom topped with a screen, on top of this screen is some aragonite sand followed by another screen. On top of this screen is some more aragonite sand and then the live sand. All of this is supported via some pvc piping to take the weight and create the plenum space.

In a plenum system it is recommended that little or no water flow be directed across the surface of the substrate. It is also recommended that a protein skimmer be utilised with a plenum as this will assist in the removal of any dissolved organic compounds which are not removed by the plenum.

It is easier to introduce a plenum to a new aquarium rather than the modification of an existing one. If you are interested in introducing a plenum to an existing system you will either have to remove everything from the display aquarium to introduce it or build a plenum in a separate aquarium and attach it to the system using overflows and pumps.

As with the introduction of any filtration device you will need to monitor the water parameters carefully so that you know that the nitrogen cycle is functioning properly.

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Tags: Aquarium Filter, Aquarium Filtration, Care, Equipment, marine-aquarium, saltwater-aquarium

What Is Natural Aquarium Filtration

There is one thing that I have learnt in all my years of keeping aquariums - do not underestimate nature!

It still amazes me today how powerful natural aquarium filtration actually is and how many ways there are to actually filter an aquarium or provide additional nutrient export by using the power of mother nature.

Nowadays whenever I am asked for my recommendation as to the best way to filter a marine aquarium I always mention natural filtration. In my opinion and this is purely my opinion live rock mixed with a remote deep sand bed has to be the ultimate natural based filtration available at this moment in time.

The prime advantage of using natural based filtration methods is its efficiency and the advantages that it gives to the aquarist.

A lot of people however have never heard of natural filtration never mind actually understand what it is.

So what is natural filtration?

Any filtration technique applied to an aquarium actually does have an element of nature in it - the bacteria however in a lot of occasions the container upon/in which the bacteria lives is not natural - it is manmade.

A good example of the above would be a canister filter. The bacteria is natural, however the holding device if you will has been manufactured.

Therefore a good way to explain natural filtration is that it is where the bacteria live in any area which has not been manufactured by man.

This is not a set rule however as there are exceptions to natural filtration. One of which would be using macro algae as a nutrient export tool.

Numerous natural filtration methods can be employed in the home aquarium. Some can be implemented for use as a primary filtration method whilst others can be utilised as an additional nutrient export tool.

As already stated natural filtration can be and is an exceptionally powerful tool. Think about the ocean - it is huge, however the natural filtration devices which are in use in the ocean are very similar to what we can use.

The rock structures on the coral reefs are similar to live rock filtration, grass beds are similar to a refugium/macro algae, mangrove swamps are a much larger scale of mangrove usage in the aquarium etc.

Can you see how powerful this type of filtration can be. The ocean has been filtered this way for millions of years and it can and does work in the aquarium.
Although our aquarium are minute compared to the size of the worlds oceans the end result is the same - excellent water parameters.

There is a point which needs to be made however, the filtration has been termed as natural filtration simply because it is similar to what is used in nature or is the same as is used in nature but on a much smaller scale but there will always be an element of human involvement.

That’s right - the care and maintenance. As with all things in this hobby the correct care and maintenance techniques need to be applied and this is no different with natural aquarium filtration. Nature can again be involved in this area for example using hermit crabs, snails etc to keep the rocks/sand clean however there will always be a time where we need to get involved to keep it just right and running at optimum efficiency.

If you are just starting out in this hobby or already have an aquarium and are using man-made filtration then I really recommend that you at least consider natural based aquarium filtration. It is absolutely amazing how powerful it actually is.

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

Cryptic Zones - Another Filtration Possibility

There is a scientific term used which is called ‘the gradient concept’. This term basically describes how various marine organisms can be graded according to the amount of light which they receive.

There are two zonal categories which are most commonly used, these are the exposed and the semi exposed zones.

The exposed zone is an environment which is in shallow water and receives a lot of strong sunlight. This is the zone which is typical of the upper reef, otherwise known as a shallow reef. The water currents in this zone are normally quite fast and chaotic, therefore any organisms which live in this area have to be able to withstand such high currents. Due to the high currents there is normally a lot of suspended matter moving around in the water; however with the strong water current a lot of the filter feeding organisms struggle to extract these from the water. This zone is where the majority of the light loving high current SPS corals live and is effectively the environment which we attempt to replicate in the majority of our reef aquariums.

The semi exposed zone is similar to the exposed zone but both the light and water currents are considerably less. Because of the lower water currents filter feeding organisms are able to extract the particulate matter from the water more easily. This zone is similar to that of deeper reef conditions, and is otherwise known as the back reef. In this zone there are still a huge range of photosynthetic organisms which can survive but this zone, because of the lower light conditions, also provides the non photosynthetic organisms with a place to thrive. Again this environment can easily be replicated in our reef aquariums.

In the marine aquatic world there are effectively three more zones which are:

1. Semi Cryptic
2. Cryptic
3. Filter Feeding

The semi cryptic zone is the zone which occurs in the sections of the reef which are either deeper down the face or in naturally occurring overhangs in the reef structures. This zone has a very low light level and can only support photosynthetic organisms which can survive in this type of area.

The cryptic zone is the zone which occurs in the sections of the reef where light if any is far too weak to support any photosynthetic organisms in any way at all, and can only support non photosynthetic organisms. In the natural reef this occurs either within caves or deep into the overhangs of a reef structure.

The filter feeding zone is effectively a combination of the semi cryptic zone and the semi exposed zone. The difference in this mixed zone is that there is little light but very strong water currents, therefore particulate matter in the water can be delivered and consumed via the various filter feeding organisms. This zone is normally where the non photosynthetic soft corals occur.

Understanding the differences between the zones enables you to be able to see what zones you currently have in your aquarium - you will be surprised as to how many you actually have. You will probably find that you have many or even all of these types of zones in parts of your aquarium, however some may be quite small - e.g. small caves in the rock face.

You need to consider these types of zones when setting up a new reef system and also when introducing corals into the aquarium. When purchasing a new coral you need to understand the requirements of the coral and ensure that you have an area of the correct zone available in your aquarium to support it.

In your aquarium you will have various zones in various sizes, however one which is a valuable addition to the aquarium is the implementation of a designated cryptic zone.

A designated cryptic zone can easily be implemented into an existing system by adding a new aquarium into the system, possibly next to the sump, in the sump etc. This aquarium is filled with aquarium water via an overflow from the main aquarium or a tee off from an existing overflow. A small amount of substrate needs to be added. On top of this substrate is placed some pieces of live rock, sponges, sea squirts, non photosynthetic corals etc - effectively any non photosynthetic organism which can survive in a cryptic zone. The aquarium should then be effectively covered up to prevent any light from entering. Dirty water (un-skimmed as DOC’s are a requirement in this area) is fed to this aquarium at a very slow pace and there is minimal water current. This un-skimmed water is best fed into the cryptic zone along the top of the water. What this does is allow the particulate matter in the water to slowly settle down onto the organisms so that it can be consumed. The matter also falls onto the substrate. This allows for the growth of the organisms and therefore more removal of particulate matter from the water. Water from the cryptic zone normally overflows down to the sump so that it can be skimmed therefore for this reason you will need to install the cryptic zone aquarium higher than the sump so that it can overflow. It is also advisable to add some types of cleanup crew into the cryptic zone aquarium so that they can deal with any particulate matter on the substrate, rock work etc.

I have seen various designs of a designated cryptic zone in use. Some have even been combined with deep sand beds/plenums. Occasionally if you open up the covers and have a look you will be amazed at the life which is growing in there and how fast it grows. The thing I like about a cryptic zone is that sponges can quite easily grow. Sponges are a good filtration tool and utilising a cryptic zone will afford you the opportunity to grow some of them.

Of course more than one zone can be implemented whether this is directly in the display aquarium or by using external aquariums.

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Tags: Aquarium Filter, Aquarium Filtration, Care, marine-aquarium, saltwater-aquarium

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