The Fluidized Bio-Filter

Bio-filters in marine aquariums are of enormous importance. Without the nitrogen cycle that is provided by Nature all aquarists would soon be in trouble. All those bacteria working away so industriously are doing us all a favour.

Bio-filtration, or the life support system as some aquarists call it, comes in several guises. The current best is live rock, whether that is aqua cultured or from the ocean. The rock from the ocean offers the possibility of a greater diversity of life in addition to the desired bacteria, but this includes of course unwanted life, such as certain crabs and shrimps, not to mention aiptasia anemones (now aren’t they just every aquarist’s favourites!).

Then there is the canister filter, a device that has been in use for many, many years. They are much improved nowadays with much easier access, meaning that most have got rid of those fiddly little clips that used to be used to keep the lid on. Most come with removable chambers thus making the insertion of media for mechanical, bio or chemical filtration easy. The canister is really well proven and highly reliable. Though not often thought of this way, they really operate a ‘closed loop’ when connected.

There is a further piece of equipment that isflui designed for bio-filtration, but it is not so well known. This is the fluidized bio-filter. Basically the device is a tube usually constructed of acrylic, with an inlet at the bottom and an outlet at the top. Inside is a quantity of sand – not just any sand but a type that resists wear in the tumble action it has to endure. A pump or powerhead is connected to the bottom inlet and the outlet at the top is fed back to the aquarium, usually at the opposite end. Sometimes the device is supplied with an inlet filter to help keep the sand clean, but if not it is easy enough to put a foam filter on the pump or powerhead.

As the seawater is pumped through the sand, the sand is ‘fluidized’. This means that the flow of seawater pushes the sand upwards with enough force to keep it loose, but not enough force to make it hurl about the tube. The result is that each grain of sand presents all of its area for colonization by bacteria. Such is the area that a fairly small unit can deal with a fairly large aquarium. Of course this also depends on the bio-load – a fish only system usually presents a larger load than a reef system.

The downside of this type of bio-filtration is that the nitrogen cycle will operate very efficiently, the bacteria converting ammonia to nitrite, then nitrite to nitrate, but it stops there. So nitrate will slowly build up in the seawater degrading its quality. This also applies to a canister filter.

The fluidized bio-filter is a perfectly viable alternative when a system is being considered. The units are usually ‘hang-on’ and easily fitted. The sand in the tube tends to degrade over a long period and the manufacturer often puts in a small bag for replacement purposes. The manufacturer will also advise the flow rate that is required to fluidize the sand correctly.

It is important that the aquarist maintains good general seawater circulation in the display aquarium as the bacteria that inhabit this type of device depend on the seawater’s oxygen content, in the same way as a canister filter and live rock. Also, in addition to the other benefits, routine seawater changes are required to control any nitrate build up.

---

Oh, no, nitrate…

…and I don’t know why. I’ve live rock and everything seems fine at the moment, but I’m worried..

These words are quite understandable. Over and over again mention is made of seawater quality and how important it is – in fact seawater quality is the number one requirement, ahead of lighting (for a reef aquarium). So concerns in this direction are quite correct.

First, without being over scientific, what is nitrate? Every aquarium in order to be healthy needs a biological support system, commonly called a bio-filter, though some aquarists call it aquarium life support. This filter when functional is loaded with bacteria. The life processes of livestock and the rotting of uneaten food, algae and the like creates toxins, the first of which is ammonia. This is deadly to livestock. Bacteria within the bio-filter convert the ammonia to nitrite, again nitrite is a toxin and nearly as deadly as ammonia. Other bacteria then convert the nitrite to nitrate which in general is not toxic, but detrimental to seawater quality at too high a level. The bacteriological process has the overall title of ‘The Nitrogen Cycle.’ This cycle under certain conditions continues when nitrate is converted to gas which escapes from the aquarium, but here the concern is nitrate.

In the aquarium, whatever type it is, ammonia, nitrite and nitrate are being continually produced. The production is at its highest in a fish only system, as fish consume relatively large amounts of food which enters the Nitrogen Cycle process. Reef systems have lower fish loads, but nevertheless the same applies. The bacteria are continually hard at work.

The guideline that is given for nitrate when tests are being done is 10ppm (parts per million) or less in a reef system, and as close as possible in a fish only system. Why ‘as close as possible?’ It is more difficult to maintain a low nitrate presence in a fish only system because, as previously stated, there is a higher fish load and consequently heavier feeding. Why is the level stated more strictly for a reef system? This is because there are corals present and these are generally more sensitive to nitrate than fish. Note that some fish are more sensitive which should be noted in research before purchase.

Just to wander off the point a moment, there is something else that is interesting as well. I have never encountered this problem. A good while ago a well-known aquarist was asked in a magazine why a recently purchased fish, stated by authorities to be ‘reasonably hardy’, on introduction to a fish only system died. All the other fish present, some considered to be less hardy than the new addition, were fine. After a considerable amount of head scratching, it transpired that the nitrate reading in the seawater was approaching 150ppm. A little high in anyone’s book! There wasn’t any mention of problem algae which was fortunate for the aquarist. The fish that were already in the aquarium had been there from the word go or a little later. It was also discovered that seawater changes were done very spasmodically. So why did the new fish die? It had been purchased from a retailer whose seawater quality would have been at least reasonably good with low nitrate. The fish had then been introduced to very polluted seawater and had succumbed. What of the other fish? These had been in the aquarium for a long while and the nitrate level would have risen slowly. So they had become accustomed, or perhaps it is better to say ‘hardened’, to the nitrate presence. The advice was to carry out regular seawater changes and bring down the nitrate level, but not too quickly in case of any affect on the resident fish.

I bet that problem doesn’t happen very often. Anyway, back to the text.

There’s nitrate present – what to do? If the nitrate is within the guidelines, then perhaps it could be lowered even further by a small increase in the amount of seawater changed at routine changes. It is when it is quite high that is of most concern. The seawater needs to be of high quality and there isn’t any desire to tempt fate by providing nourishment for nuisance algae.

The first action is to attack the problem by, as just mentioned, increasing the amount of seawater changed. The basic general guideline for routine seawater changes is 10% of the net gallonage in the whole system but this can be flexed according to need. It is best not to increase the amount above 25% (severe cases) as the ‘raw’ seawater in this quantity isn’t always happily received by livestock. Increasing the amount changed increases dilution. The level should come down slowly until it is acceptable. The continuous addition of food and presence of livestock means that the Nitrogen Cycle is ever active (as it must be), so routine seawater changes should continue. After the following, if a cause of excessive nitrate is found the amount of the changes could be reduced again.

The above is treating the effect but what about the cause? It is best to start from square one and work through. There isn’t anything difficult in the process.

Excessive nitrate is in the seawater, but could it be getting in before any seawater enters the aquarium? First, have a look at the dry salt mix in use. It would be unusual with modern salts for there to be any nitrate (or phosphate) presence, but check that this is so by looking at the manufacturer’s information. Often the dry salt package will advise the salt is nitrate and phosphate free. In the unlikely event it isn’t free of these pollutants, change the brand to one that is.

The dry salt has obviously to be mixed with fresh water before use. It is highly recommended that RO (reverse osmosis) water is used, which is tap water that has been ‘super filtered’ to remove any unwanted substances. If RO water is in use, do a nitrate test to see if the unit is functioning properly. If there is a nitrate presence, then the heart of the RO unit, the membrane, may have a problem, and this should be checked. It may mean the purchase of a replacement unit.

If tap water is in use and not pre-filtered, then the same thing applies – test the water. In some areas tap water is fairly pure with a very low nitrate content, but in other areas it may not be. These areas are often agricultural where there is a lot of fertilizer in use (including nitrate), or industrial. If it is found that there is a nitrate presence, particularly a fairly high one, then it is best to invest in an RO unit and be rid of the problem. There isn’t much point in introducing nitrate when fresh seawater is mixed after the manufacturer has taken the trouble (which the aquarist pays for) to ensure the salt is nitrate free.

The next checks concern the aquarist’s husbandry disciplines. The aquarist can quite easily be over or under enthusiastic in some areas.

The first area to consider is feeding, where the majority of new aquarists overdo it. Overfeeding is fairly difficult to avoid by an experienced aquarist, as it is hard to ensure that all food goes where it is intended. The new aquarist is often over-anxious that the livestock get enough to eat and consequently too much food gets into the system, much of it is not eaten, it rots and joins the Nitrogen Cycle. This cycle as already stated produces nitrate. As a point of interest, as with nitrate, phosphate is linked to nuisance algae outbreaks. Guess how the majority of phosphate gets into the seawater – yes, with food. So it is very important not to overfeed. There are a few guidelines on feeding techniques to look at, including one under ‘Articles’ on this site titled ‘Food For Thought.’ Allowing a little time to learn how to feed and ensure the fish have enough, and at the same time avoid overfeeding as far as possible, is very worthwhile.

The second discipline that needs to be looked at is maintenance. Some aquarists like doing this (as some gardeners like weeding) and some do not. I don’t completely enjoy it, but do it willingly because the appearance of my reef, meaning the health and vitality of my livestock, depend on it. So how does maintenance have any effect on nitrate?

Good seawater circulation usually means good oxygen content. Oxygen is taken in at air/water interfaces, particularly the seawater surface in the aquarium. If circulation is at it should be oxygen content should be adequate. The bacteria that convert the toxins ammonia and nitrite are very reliant on oxygen availability in the seawater, so if there is plenty always available then the bacteria are able to function efficiently. This produces nitrate as previously mentioned. If live rock is used in the aquarium, and the oxygen loving bacteria are producing nitrate, then the nitrate converting bacteria convert it to gas, which easily escapes from the aquarium because of the good circulation. So the aquarist needs to ensure that circulation is adequate. Lack of good circulation could be a design error in a new aquarium, or in an established one the result of coral growth blocking seawater flow, or powerhead intakes being clogged with detritus, or tubes becoming narrow with detritus build-up. Checking these is part of ongoing maintenance. Intakes can easily be checked visually and the inside of tubes occasionally – seawater output, or the lack of it, could indicate tube blocking.

Detritus itself is a normal entrant to the aquarium. When maintenance is being done detritus should be removed as far as possible. This removal helps prevent rotting substances from entering the Nitrogen Cycle in the first place, thus not producing any additional nitrate. If detritus is heavy an investigation should be made to find out why and hopefully remove the cause. Seawater circulation usually means that detritus tends to settle in one or two particular areas, usually where the flow is lower. When a routine seawater change is done this detritus should be siphoned out.

Detritus can also settle like a dust on live rocks, or any rocks for that matter. It is a good idea to remove it once in a while. How can that be done? Obtain a baster (as used in a kitchen) or similar and gently pump seawater over the rocks. This will put the detritus in the seawater column and hopefully permit either a mechanical filter to extract it, or make it settle in an area where it can be siphoned out.

Another area to check is a sand bed. This sand bed could be in the display aquarium or in a sump, though in this case the sump is unlikely – unlikely because the sand bed here is one for decorative purposes only which would not normally be in a sump. The decorative bed is usually 1 to 2″ deep and made up of coarse coral sand. They can be very attractive. They can also get very dirty, as detritus settles into the sand bed between the grains. This is unwanted and the detritus should be removed by using, for example, a gravel cleaner on a reasonably regular basis – at least when the sand starts to look dirty. A dirty sand bed is not attractive anyway so the aquarist should notice it. (Note that only a decorative sand bed should be cleaned, not a DSB (deep sand bed))

Finally, nitrate can be produced in excess by the livestock, particularly fish. Not directly of course, but because of their life functions and the food that has to be offered. So it is important not to overstock – the more fish the stronger the pressure on seawater quality. More fish, more food and the harder the bacteria work. Normally they’ll do their job well, and normally they’ll work 24/7 on everything suitable and available.

---

Prepare Your Aquarium By Cycling It

It is essential to have efficient biological filtration in any marine aquarium. This is the bacteria based ‘filter’ that converts dangerous toxins so that the livestock are not threatened. Some aquarists prefer to call this bacterial function ‘life support’ and this name seems appropriate. Without it, or with insufficient, the livestock would die or at least be sickly.

Biological filtration occurs in an area where bacteria can live and perform their functions. The most essential bacteria need a plentiful supply of oxygen and a suitable media. The bacteria will not only live in and on the media provided by the aquarist, but on many surfaces in the aquarium. The media is the main area though.

There are different ways of housing the bacteria. One of the best ways, probably the best, is to use live rock. This is rock that has either been harvested from the wild or aqua-cultured and already contains a population of bacteria. Another way is to use a container, for example a canister filter, to provide a home. This kind of filter requires suitable media.

So what is this ‘cycle’ of the aquarium? It refers to the Nitrogen Cycle, which is the overall title given to the actions of the bacteria that are so important. Basically, ammonia is produced by livestock and is lethal. Bacteria convert the ammonia to nitrite, another toxin that is nearly as lethal. More bacteria convert this nitrite to the generally non-toxic nitrate.

Live rock as said already contains bacteria, so perhaps there isn’t any need to ‘cycle’ it before use. This in theory is correct; however care needs to be taken. Live rock will normally be purchased from a dealer, and it will have been ‘cured’ (that is, given time for all the dying life on and in the rock to clear). Once the curing is complete the rock is ready and has a good bacterial load. However, as with all life, bacteria need food. For the most part, cured live rock is placed in aquariums or vats awaiting sale and is not fed. Over a period of time, the bacterial population reduces. It is important therefore not to assume that just because live rock is in the aquarium all is well and fish can be added. The bio-load, particularly fish, must be added slowly over a lengthy period of time so that the bacterial population has time to adjust. Failure to do so is likely to result in major problems or disaster, as the bacteria that face a bio-load that is too large cannot develop their numbers quickly enough, and therefore cannot deal with the amount of toxic ammonia that is present.

If the aquarist is to use a device such as a canister filter then, as said, a suitable media is required – this type of media is readily available. In this case, the media will not contain any bacterial life whatsoever and it is up to the aquarist to kick-start it. This is easily done.

It used to be achieved, and this method is still sometimes recommended, by placing one or two hardy fish in the aquarium. These fish can hopefully withstand the rise in ammonia until the bacteria become established and deal with it. However, this method is not recommended. It is unethical to subject any life form to unnatural and stressful conditions.

Instead, the method recommended is to purchase a bottle of commercial maturation fluid. These are readily available and not expensive. The instructions should be followed carefully. Basically, the aquarist is introducing ammonia into the aquarium which of course is food for the first bacteria that will deal with it. It takes time for the bacteria to develop and a test kit is used to monitor the ammonia level – when it reaches a certain point additions of the maturation fluid are stopped. There will eventually be a drop in the ammonia level and another test kit will detect nitrite. This means that the cycle is beginning – bacteria are converting the ammonia. Then nitrite will start to be converted. Monitoring continues until tests read zero. Sometimes levels fall slowly but often they suddenly drop. This is because the bacteria population is large enough to deal with all the toxins present. At this point the bio-filter is said to be mature, meaning it is capable of supporting life. However, it is still unstable and stocking of the aquarium needs to be carried out slowly to allow the bacteria to adjust.

One point about maturing a bio-filter using maturation fluid. As said, bacteria convert ammonia to nitrite, then nitrite to nitrate. Nitrate, though not generally toxic, is undesirable and reduces the quality of the seawater. Clearly if bacteria are converting ammonia and nitrite then nitrate is going to appear. Nitrate is easily tested for and if present in excess a seawater change will dilute the concentration. There is another way to avoid nitrate in the aquarium entirely during the maturation period and that is to use a bucket. Put seawater in the bucket and a heater. Run the seawater to the canister or similar filter and then back again. The filter can be matured this way and when done the seawater in the bucket can be thrown away. The bacteria populations are in the canister and when connected to the aquarium are ready to work.

---

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.

---

Understand The Nitrogen Cycle – Your Livestock Depend On It

Modern reef aquariums try to be as natural as possible. The modern day captive reef would make yesterdays marine aquarists eyes water – they are so beautiful in total and in detail. Fish only systems house fish that would have been impossible to keep not that long ago. This success is because of natural processes and modern technology.

Whatever type of marine aquarium is kept, reef system or fish only system, there is one function that is totally essential. It isn’t a modern natural ‘invention’ either, it applied to those earlier aquarists just as much. The difference is that in the very early days the aquarists didn’t know anything about it. Before my time a pioneer marine aquarist thought he could keep his aquarium clean more easily by using what turned later into the much used under gravel-filter. I believe his name was Straughan. He was amazed about the length of time he was able to keep livestock, and put it down to better cleanliness. Investigations showed that in fact he had stumbled onto the secret of keeping any marine system basically healthy. In a way it was due to better cleanliness.

Livestock in an aquarium continue with their normal life functions. They are fed. Algae can die and rot as can uneaten food. This protein breaks down into a deadly toxin – ammonia. In the presence of not a great amount of ammonia livestock can be badly affected or die. Fish could hang quietly at the water surface, or swim in a very erratic manner, even upside down, or sit on the aquarium bottom leaning against a rock, and breathing could be rapid. This situation is very serious.

Yet in the modern aquarium the problem of toxins hardly arises, except perhaps in the case of a beginner who does not use patience and stocks too rapidly.

The saviours and the servants of the aquarist are bacteria. These bacteria break down toxins and the process is generally known as the nitrogen cycle.

Ammonia is very toxic and is broken down by bacteria called Nitrosomonas. The toxic ammonia is converted to nitrite, which is also toxic and nearly as bad as ammonia. That’s a lot of good! Well, another bacteria then comes into play and converts the nitrite into nitrate. These bacteria are called Nitrobacter. Nitrate can be bad at high levels, but is safe in comparison to ammonia and nitrite. The nitrogen cycle does not stop at this point, but continues when the nitrate is converted to nitrogen gas. The gas escapes from the aquarium and the cycle is complete.

Simple, nature saves the day!

Yes, it does, but there has to be a catch and here it is – the ammonia/nitrite conversion bacteria need a different environment to the nitrate bacteria.

The ammonia/nitrite bacteria require an environment that provides obviously ammonia and nitrite, and in addition they need a good supply of oxygen. This oxygen can only come from the water (except in one instance) so the aquarist has to provide plenty of water circulation to ensure good gas exchange at air/water interfaces such as the surface of the seawater. The home for the oxygen hungry bacteria can be in a canister filter and the like with suitable media. What is the exception mentioned – this is the so-called trickle filter. As the seawater running down is exposed to the air, oxygen is plentiful.

Providing a suitable home for the ammonia and nitrite bacteria is easy. The aquarist needs to ensure that the canister etc filters are properly matured, and this is achieved by using a prepared commercial maturation fluid. Using test kits, once the nitrite has disappeared the filter is initially mature. The instructions with the fluid will give details which are very straightforward. The nitrite showing as cleared means that there is a presence of bacteria which will deal with ammonia and nitrite. When the filter is initially mature, stocking can commence, but with great care and patience, as the filter is still unstable and needs to adjust to the bio load placed upon it.

The problem – here we go again – with canister etc filters is that the complete nitrogen cycle is not achieved. This is because they operate in an oxygen rich environment. Bacteria that deal with nitrate can live in an oxygen rich environment too, but under this circumstance they will not deal with the nitrate. An environment must be created where there is a lack of oxygen, and in this circumstance the bacteria will turn to the nitrate. The bacteria need oxygen, and the only way they can obtain it is to extract it from the nitrate, which breaks the nitrate down.

So there is no reason why a marine system cannot use a canister etc filter. It does mean though that the aquarist must keep a careful watch on nitrate levels as well as other parameters. Routine seawater changes will control nitrate to a degree, as will good husbandry such as a proper feeding discipline. There are other ways to control nitrates which will not be dealt with here.

There is a way of achieving the full nitrogen cycle, and that is to use live rock. This live rock (LR) can be used in fish only and reef aquariums. In the reef aquarium it has the secondary benefit of providing a material with which to construct the reef.

LR works as filtration because it is porous and provides a home for the bacteria. On the surface and inside toward the surface dwell the bacteria that use oxygen and deal with ammonia and nitrite. Deeper inside, where oxygen levels are depleted, dwell the bacteria that can only obtain oxygen from nitrate. Therefore the total nitrogen cycle is achievable. It is important that sufficient live rock of good quality is provided.

Using LR the aquarist still needs to monitor seawater parameters. Nitrate is included in those parameters, as LR has limits the same as anything else. That said, it is a wonderful filtration media.

Whatever type of bio filtration the aquarist uses, the bacteria will not make many demands, and the demands they do make are easily met. Fail to meet those demands, or pass the point where the bacteria do not have the capacity to deal with toxics, and the consequences could be very serious.

Provide suitable media and well oxygenated seawater, have patience with stocking and do not overstock, and nature’s bacteria will work silently and unseen providing life support.

---

I’ve Got Bio-Balls, Will I Be Ok?

No, no, you’ve got the wrong end of the stick! It’s not some horrible problem at all, but to do with aquariums.

Marine aquariums need bio-filtration, and this is provided by bacteria. The bacteria of course need a place to live and to avail oneself of this free service from nature the aquarist must provide them with a suitable home.

The bacteria operate what is called the Nitrogen Cycle, either fully or in part. To operate in part is easy, all that is required is plenty of oxygen plus ammonia and then nitrite. The bacteria will change the ammonia to nitrite, and then the nitrite will be changed to nitrate. Ammonia and nitrite are toxic, and nitrate much less so.

To support livestock it is enough to do only as in the previous paragraph. The toxic ammonia and nitrite are dealt with. Nitrate is left and this should not harm anything at very low levels.

However, the levels will slowly increase beyond the guideline (for a reef system) which is 10ppm (parts per million) or less. One way of reducing the level is with routine seawater changes. These changes are good for other reasons and should be completed, however nitrate could increase in spite of them. Nitrate increases are not desirable as the appearance of nuisance algae may occur.

Nature has a remedy but it cannot occur where there is oxygen present in any normal amount. The bacteria that reduce nitrate need an environment that is very low in oxygen – this forces the bacteria to extract oxygen from the nitrate thus removing it (it converts to gas and escapes the aquarium).

So bio-balls are a good medium for oxygen hungry bacteria, but not for bacteria that deal with nitrate.

If nature is going to assist with nitrate reduction, a denitrator (a so-called nitrate ’reactor’) could be used. Better, live rock can be used. Live rock has surfaces that can be used by oxygen needing bacteria, and well inside are areas for the nitrate bacteria. Live rock with a DSB (deep sand bed) is even better.

So if an aquarist is using bio-balls the answer is yes, it will be all right, except that the bacteria will produce nitrate and that will be the end of nature’s assistance.

If bio-balls are in use in addition to sufficient live rock (and perhaps a DSB) then the bio-balls can be removed, but remove them a few at a time over a period of weeks. This will allow any bio-load that was supported by the balls to be taken up gradually by the other media.

If the bio-balls were the only media, then none must be removed straightaway. Introduce sufficient live rock into the aquarium, wait a week or two, then commence removing the bio-balls a few at a time as already described. It would be of little use introducing, say, a canister filter for bio-filtration as the end product is the same – nitrate.

A good few years ago bio-filtration methods included balls. Times have changed.

---

The Bacteria’s Role In The Nitrogen Cycle

In the marine aquarium, be it a reef tank or a fish only aquarium, the nitrogen cycle is of paramount importance. It is the life support function for all the livestock. Without it, or with a serious deficiency, the livestock will be in serious difficulty and face death.

In an aquarium the livestock carry on with their normal life functions and need feeding. This introduces waste into the seawater. In addition, algae etc can die and rot. The product of the breakdown is ammonium (NH4+). Because seawater is at a fairly high pH (around 8.3) some of this ammonium is present in the form of ammonia (NH3). That is the problem, ammonia.

Ammonia that is present even in small amounts is toxic – deadly – to aquatic life. Fish can display ammonia poisoning by peculiar swimming: Swimming slowly and rolling over, going up and down in a random fashion, breathing very quickly, lying at the bottom, floating around at the top etc. Varied, but if seen there can be no doubt something is wrong. If only one fish is behaving strangely, and the rest are normal, the problem is unlikely to be ammonia poisoning.

Nature is ready to deal with the problem, luckily for us aquarists. There always seems to be some kind of life that is ready to use up whatever is available, and with ammonia this is the case. The life forms are Nitrosomonas bacteria. The ammonia is used by the bacteria for energy.

So that’s fine then, problem solved. Not quite. Even though the bacteria mentioned have removed ammonia, it hasn’t been conjured into oblivion. Guess what, the ammonia has been converted to nitrite (NO2) which is nearly as toxic as ammonia. Fish reaction to nitrite is similar to ammonia.

So what we have is a cycle, as in the heading. More bacteria use the nitrite, these bacteria being Nitrobacter. The situation becomes much better after this stage, as the product produced is nitrate (NO3). This is nowhere near as toxic as ammonia and nitrite, but can cause some problems at high levels. Probably the major problem that aquarists could face with nitrate at lesser levels is excessive algae presence.

Nature however can once again come to the aquarist’s aid because, yes that’s right, bacteria can deal with the nitrate. Hang on a moment though, there’s a qualification here. It depends on the bio-filtration being used (the bio-filtration is home to the different bacteria). If the aquarist is using live rock, fine, good quality live rock in proper quantity will deal within reason with nitrate. If the bio-filter is a canister, for example, then there aren’t any bacteria present to deal with the nitrate. Why? Because the environment is oxygen rich. To deal with nitrate a nil to low oxygen environment is required. Live rock can provide this as the bacteria involved live deep inside. If the example a canister filter is in use then other means are available if required to control the nitrate.

The nitrate is removed because the bacteria extract oxygen from it, this being the only way open to them. The end gas, nitrogen, is released from the seawater at air/water interfaces.

So the whole nitrogen cycle is from ammonia to nitrogen gas. There are several ways to achieve the cycle, but whatever method is chosen (except perhaps one) there are important points for the aquarist to be aware of.

The bacteria colonies that convert ammonia to nitrite use a lot of oxygen in the process. The next stage, nitrite to nitrate, uses up a lesser amount. There is only one place that the oxygen can come from and that is the seawater. In addition to the bacteria, the reef livestock need oxygen in good quantity. So the seawater must always have a good oxygen content. Having said that, the modern reef or fish only system usually hasn’t a problem, as they are mainly open topped, often use weirs, and have good water circulation, particularly reefs. If oxygen content were ‘near the edge,’ it could be more of a problem for a fish only system because of the usually higher fish stocks per gallon. What is the possible exception mentioned in the previous paragraph? The trickle filter. Seawater is exposed to the air as it runs down through the media, which means oxygen from the air could be used (an air/water interface).

The nitrogen cycle bacteria are not present instantly. With ‘unnatural’ filters, such as the example a canister, they are introduced by inoculating the seawater with the required substances. Commercial preparations are available. Measuring the seawater for ammonia, nitrite and nitrate advises the aquarist when the bacteria colonies are working. Live rock is different, as the required colonies of bacteria should be present. Caution still has to be exercised as these colonies might have been diminished in the ocean to aquarium processes.

There isn’t any argument – the life support system, or bio-filter, or nitrogen cycle, call it whatever, must be present and effective. It will then protect the livestock by working unseen and silently.

---