Nutrient Control in the Reef Aquarium.

Getting to the core of No3 issues

Ok so lets take a cold logical look at No3 build-up in a reef aquarium...(I wont talk so much about Po4 because that is so easily dealt with by way of the many medias around and a basic fluidized reactor but the same rules hold pretty much true for this as well as No3)..

1. First of all, ask yourself where No3 comes from....simple answer (and accepting common sense that you should be using 0.0 tds RO water for top ups), it only comes from what 'you' put in the tank as food..N03 is the end product of the bacterial breakdown of what goes into your tank as food. It doesn't matter which pathway it has taken, be it direct biological breakdown, or through several stages of assimilation from fish faeces, to scavenger faeces, to micro-fauna faeces to final bacterial breakdown, the net result is No3.

2. The degree or % of food that makes it all the way to the final stage of No3 is directly proportional to the number of steps it has taken to get there.

As an example using purely hypothetical numbers meant as a means of expression, lets just say that you have a tank that has no life apart from bacteria....You feed this tank 1.0 gram of food which is then broken down. Allowing for differing chemical content and a degree of non biologically degradable content (chitinous shells in the case of mysid shrimp etc) lets just say that from the original mass, you get 0.25grms of No3 as a final by-product after degradation and assimilation through Ammonia to Nitrite to nitrate (ignoring de-nitrification for the time being)

Now take the same system and add a good cleanup crew, some fish and a good micro-fauna population. You feed your 1.0 gram of food which gets eaten by the fish. (now using a hypothetical equation), lets just say that your fish assimilates into body mass and energy requirement, 5% of what it eats, the rest is passed as faeces to feed the next animal down which assimilates 5% of the 95% that the fish excreted, and so on and so forth, passing through several different mouths as it goes including your corals etc... The net result of final N03 after all these assimilatory paths will be significantly lower than the original 0.25grms that were left over in the purely biological pathway. Maybe less than half, which would explain why older UGF systems with non live rock that utilized mainly biological breakdown and very little in the way of micro-fauna, nearly always had high nitrate levels regardless of the fact that there was still a good proportion of de-nitrification going on in quiet corners and inside porous rock such as Tuffa etc....the net result and % of food input broken down directly or via 1 pathway (the fish) was significantly higher than in more modern/diverse systems...effectively these systems had a significant 'imbalance' between input, assimilation and de-nitrification...hence a pool of N03 sitting in the background.

Surprisingly, apart from the advent of DSB's and SSB's, there hasn't actually been much of an increase in total de-nitrification capacity in your average system since those days. Even with the advent of LR, there is little difference between the porosity of real LR and that of older Tuffa...both have similar capacity for bacterial colonization be that nitrifying or de-nitrifying. And UGF's actually weren't that good in most cases at staying clear and high in 02 concentration....They were frequently a hotchpotch of free aerobic channels mixed with more compact and low 02 de-nitrifying zones. its just that they clogged up more and more over time with waste, and nothing in the way of micro-fauna to free them up hence why they were abandoned for alternate methods.

The overall net result in many cases, is that 'lack' of 'de-nitrification' is not the systems downfall....Its simply that the % of input making its way to N03 uninterrupted is far greater than the system can cope with.


So how can you get things back in balance.

Well first of all, remember our No1 goal...To limit as much as possible the amount of food input that makes its way past our animals strait to biological breakdown....Food that gets eaten is good....food/faeces that doesn't get eaten is bad...

1. Look at your feeding regime....study the animals you have and their feeding requirements. In a large number of cases i have seen, the foodstuffs added to a system are not that compatible with the animals they have. most commonly particle size and type...Look at your animals at feeding time. how much of what you feed actually gets eaten and how much goes strait over the weirs. do you drop flake on the surface or do you push it under the surface where the fish can get at it easily and it stays in suspension for longer rather than drifting across the surface to be sucked over the weirs to breakdown in your sump.

2. Older more diverse and well established / grown out systems, are far easier to feed small particulates to than younger systems without it going to waste...There are many more mouths to catch passing food, and many more to take advantage of excretions further down the line. So the real task is to keep food input relative to the amount of livestock that can take advantage of it throughout the systems lifespan. Boosting food input slightly as a means to boosting critter diversity is allowed but should be kept realistic. equally the opposite is true and stocking should be done at a rate where the micro fauna can keep up with the increasing food input and subsequent waste generation.

Analogy time: When your dog takes a dump on your 10x10 lawn, a host of animals from worms to beetles to larvae etc that inhabit that area all get to work on it to break it down quite quickly...It may well be the case that within a week or so, there is nothing left,....Now, how long would it take if an elephant did a dump on your lawn and the same population of scavengers had to work on that...The point here, is not the size of the dump...Its the sudden difference in how much there is to deal with and how little time the scavenger population has had to grow to take account of the increase..

The same applies to a closed system....stock slowly and the critter population which steals from the nutrient reserves, will grow and reproduce to keep up with the increase...stock too fast and you offset this balance leading to more waste 'not' being utilised...instead, it breaks down biologically giving rise to an N03 pool.

So, rule number 1: As soon as you 'start' to see a rise in N03, stop adding stock and more food....give the system and the biodiversity time to catch up...chances are that within a month or so without adding anything else and as long as the bits Ill get to later are in order, N03 will start to decrease again and you can add your next additions. If you must add anything during this time, make it 'workers', i.e. something you don't have to actively feed. i.e. cleanup crew/scavengers/ filter feeders etc...anything that 'helps' the system by stealing free waste or particulates.


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So, to have a very quick recap on section 1. we need to remember the following points as a foundation for understanding N03 and Po4 accumulation and its causes.

1. Accumulation at its most base level, is nothing more than an imbalance between the amount of nutrient added to the tank in the way of food. And the systems ability to utilise that nutrient in a manner that locks it away by assimilation or breaks it down to a final harmless substance as in the case of N03 to nitrogen gas....Effectively, what you 'see' in a test kit reading, is a representation of that state or balance. with near zero showing an ideal balance, and any number above showing an increasing mismatch between addition and removal.

2. The first course of action when dealing with rising nutrients and by far the easiest thing to change, is to look at the types of food added to the system to ensure we have a good match between 'what' we feed and what our livestock and other fauna 'prefer'. Feeding the wrong types/sizes of food at the wrong times in the life of the system simply leads to higher levels of nutrients that need dealing with at a biological level, rather than being utilised for beneficial roles such as assimilation in the fauna and micro fauna population. Equally, we can look at 'how' we feed....could we feed certain corals like LPS directly to minimise food going to waste, Do we even 'need' to feed that Fungia a whole lance fish every week, when its already in an ideal spot to pick up detritus and uneaten food that washes across the substrate (a diet its actually more attuned to receiving in the wild).?

3. Finally we have system maturation and long term development. All micro fauna populations take time to multiply when the conditions are conducive to reproduction. Conditions in young systems are notoriously unstable initially, so we should accept that despite efforts on our part to boost these populations by way adding that extra pinch of food which whilst correct to a degree, should still be taken seriously and in a controlled manner. Equally, stock additions should be in balance with the systems growth rate at a nutrient cycling level. Adding stock too quickly means more waste generated and more food put in than the system has had a chance to grow to handle in the short time the system has had to adapt...Ultimately, regular weekly testing and observation of chemical trends will show exactly where the systems balance lies, and should dictate the rate and scale of future additions.

(As a footnote here, I'll point out that the term 'heavy feeding' is relative to the individual system....It doesn't mean 'swamping' the system with food during a single feeding period. what it actually means is to feed the system to a degree that the system is running on the 'edge' of nutrient accumulation, but not 'into' it. I.e. It is a feeding method that takes 'time' to instigate on any system, building up slowly through observation and testing until you know exactly how much food you can physically add to the system to maximise both stock and micro fauna health and reproductive capacity without putting it over the edge into nutrient accumulation...99% of the time, splitting the overall daily input into several smaller feeds heralds far better results than swamping the system with one big feed per day.)


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So with control of the input. lets now look at what to do with it whilst its in there.


By and large once the right food is in the system in the right quantity and we have satisfied ourselves that we have a decent cleanup crew, we have only two priorities within the system as a whole.

A. Keep the food we add and any excrement generated by the animals within the system moving around to minimise the % that settles out and gets a chance to breakdown biologically. (its actually quite surprising just how fast food breaks down in the warm and wet environment of the reef tank) this also carries food to those animals that cant go hunting for it. The longer it stays in suspension, the more chance there is of it being snaffled up by a hungry polyp/fan worm etc. Whilst we do want 'some' degree of settlement to satisfy and encourage those critters that scavenge across the bottom, it shouldn't be too much. Remember that there is more than enough excrement making its way down there from the animals above in the first place, and these critters aren't that fussed about its origins, its all food at the end of the day, whether we find that thought appealing or not.

In conventional reefs i.e. those 'not' emulating biotope areas such as Lagoons or reed flats, circulation should be strong enough to keep particulates in suspension, but not so strong that it persistently upsets substrate layers causing a dusty environment. In general, persistently dusty tanks have an increased chance of the Lr clogging over time, reducing habitable area for de-nitrification within the pores of the LR and making life a misery for the critter population that is trying to feed on food and faeces that is being smothered by it. Personally id always say that the best method of circulation is one that not only moves water around the aquarium on a lateral plain or gyre motion, but also one that exchanges water from the bottom of the aquarium with water at the top and visa versa. Waste that just circulates around in a big circle rarely makes its way 'up' towards the weir as gravity inevitably carries it downwards in a long spiral until its just swilling around on the bottom. Ultimately you need to be able to move waste from the bottom of the tank, to the top, so it can make it to the weirs for extraction or to the intake of a pump in the case of hang on skimmers etc..

B. Once that food or waste has made its way 'out' of the tank via the overflows, our job then, is simply to minimise the chances of it making its way back up to the main display. so next I'll cover my best tips for maximising that area.

1 Skimmer: (and this is about the only bit of advice I will give here that has any chance of costing you money) . Always place the intake to a skimmer at the 'leading' end of your filtration chain. i.e. where water 'first' enters your sump or direct from the overflow pipe in the case of gravity fed designs. This is where you stand the best chance of removing the majority of waste before it gets a chance to pass through the rest of the filter system and any bio filtration that will just break it down. When set up correctly, Skimmers are actually quite good at removing quite large particulates which get stuck to the greasy coating of the foam, so they are ideal as a first line filtration method. The outlet of the skimmer can be placed wherever you like, as long as its downstream from the intake to avoid recirculating already filtered water.

Equally never under estimate the value of a correctly rated skimmer. By and large, bar only 1 or two top end manufacturers that I'm aware of, nearly all skimmers should have their maximum rating halved in the real world. Make no bones about it...unless you run a system designed and dedicated to running skimmerless, the skimmer you do buy, will be the single most valuable piece of kit you will ever use on your system...many experienced guys would go as far as saying that its the backbone of a good reef system or Berlin system specifically. so make it a strong and effective one without fear of overdoing it.. If its rated to 200 gallons, halve it and that gives you a number to work with as far as the system size goes.....if your going the other way and have the tank first, Double its size and look for a skimmer of 'that' capacity as a good match.....I kid you not.. skimmer capacity matching is where so many systems fall down...

As far as running the skimmer goes...set it it up right, Not too wet, not too dry. and clean it weekly without fail. including the riser tube, and main body if it becomes dirty on the inside walls. also clean the injectors/venturi's weekly as well. Skimmer efficiency drops rapidly as a skimmer starts clogging up. As it drops, you are effectively running a smaller and smaller skimmer....Hence my point above about capacity...If you have a good skimmer to start with, you can drop down in efficiency between cleanings without dipping 'below' the systems minimum skimming requirements.

2: Flow rate through the sump...More isn't necessarily a good thing. I've found over the years that flow rate/velocity through a sump can have quite marked effects on how well a system handles nutrients. Too fast and waste just whooshes through without anything getting the chance to pull it out of solution or for it to settle out to any significant degree in the case of DSB's etc....Too slow, and any biological filtration present will slowly become smothered with silt and suffer low 02 availability, making it difficult to carry out sufficient biological action. On the whole, regardless of system size, I've found a rough average of between 6-10X the 'tanks' volume/hour (not system volume) through the sump, is about right...this is fast enough to take a good portion of free waste from the main tank via the overflows and let it get worked on by the filtration system but not 'so fast' that you are sucking all the food out of the main tank before it gets a chance to be eaten, and not so fast through the sump that its through and back to the tank as quick as a flash to just breakdown in there again.


3: LR in the sump...On the whole, I've never come across any significant proof nor need for LR within a sump system on a sensibly stocked / fed and well managed system...But that's not to say it cant add a valuable boost to the nutrient cycling capabilities and critter generation of some systems 'if' its handled and utilised correctly...The first thing to remember about LR, is that it doesn't like silt build-up and most of the critter population spends most of its life trying to keep it that way...As a bio media for reducing nitrate levels its great as long as you keep it clean and free of detritus, so my best advice when using LR or LR rubble in a sump, is to only feed it 'pre-filtered' water that has a good dissolved organic content, but a low level of particulate matter or turbidity...In this respect, the best method by far is to separate it off from the main flow and feed it via a separate feed after some kind of pre-filter or micron bag. in this area we will also need to increase flow locally by way of a power head or such, as velocity = diffusion in the case of LR...More flow = better diffusion= better de-nitrification.... If it must be used in line, then place it after other methods of filtration that are designed to handle solid waste better, such as assimilation beds etc.

4: Refugiums : algae/Cheatomorphyllia etc. Much like LR, algae beds work much better with clear water and a good flow rate. This prevents the algae clogging up with detritus which inhibits both chemical exchange and photosynthesis. a simple rule of thumb: clear water, good flow rate and good light...That's they key to a successful and efficient algae bed or algae scrubber.

5: Sand Beds: I wont go too much into this as I'm sure most of you are sick and tired of my inane rambling on this subject, suffice to say the best results I've had come from following a few simple rules..( this refers to true Deep Sand beds and not Bucket DSB's that work on differing principles )

A. grain particle size should be sugar fine or silt like in texture and aragonite in nature.
B. A beds efficiency is directly proportional to the amount of critter life it has present the more the better.
C. flow rate across the bed can vary, but needs to be slow enough that particulates settle out as food for the critter population, without being so slow that the bed suffocates (remember that skimmer outlet that's high in 02...well now you know where to stick it to get the best of both worlds)
D. Sand beds take time to mature, they aren't an excuse to stock too quickly. although they are supremely efficient waste cycling units, they take time to develop, and take time to adjust to increasing loads...

6: Trickle filters/ and fluidised bed sand filters: Lets face it...trickle filters etc were originally designed for one purpose and one purpose only. To minimise the risks of ammonia poisoning in commercial systems that have massively fluctuating stock and food loads from one moment to the next, and for FO systems that had extortionately high stock ratios and feeding demands. As converters of ammonia to nitrate they rule supreme....as a 'balanced' method of waste control in a reef aquarium they are bloody awful. The simple facts are that if you are using one and have No3 levels below o.9ppm, then chances are you don't actually 'need' it....and if you are over 1.0ppm, chances are you would be better off without it. If you have high No3 levels above 10ppm, then chances are its the trickle or sand  filter that's causing it. (sorry if that offends anyone)


To surmise this whole topic, I'll add a bit of logical reasoning.....If after all the info above, you are 'still' having issues with high N03, then I'd be tempted to point the finger squarely at stocking ratio or stock 'type' for the volume of water available and the filtration/skimming capacity to hand, seriously, be 'brutally' honest with yourself...are you simply asking too much of your system... The only other issue within the hobby at present which does occasionally ring alarm bells with me, is the use of large amounts of Reefbones in some systems. after seeing cross sectional segments of this stuff and noting just how much internal life is left to dry out and die off (the number of boring molluscs I've seen in some pieces is astonishing) I'm wondering what the long term affects are of all that matter is as it takes on water once put back into a system, starts rotting like some reconstituted pot noodle and starts leaching out.....maybe not so bad if added in smaller doses to older more established systems, but I'm not that convinced its that great in new ones that don't have a critter population sufficient enough to deal with it strait off before it gets infested with those initial algae blooms so common in new systems...so that may be worth some extra consideration..


Equally, I'll add that I haven't written this as a response to try and tempt people away from alternative methods of problem nutrient control via vodka dosing etc, and I'm not saying its 'wrong' to do it....All I'm saying here, is what I said earlier...If you have a well planned system that uses the right kit, in a logical and educated fashion mixed with sensible stocking and an educated approach to feeding, regardless of whether you are a heavy or light feeder, then chances are you'll fall into that enviable group of people who never even give No3 a second thought apart from a 'done for the sake of it' weekly/monthly test, and Po4 whilst being of more importance, still isn't a test that's dreaded..

Many thanks for reading