Marine aquarium biological filtration,explained.

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Marine aquarium biological filtration,explained.

Post  Admin on 19th September 2009, 9:57 am

Nitrogen cycle biological media, how does it work!

Once the affects of fresh sea water or water from a matured aquarium has enacted upon enate surfaces, you have broken what may be called a type of surface tension, until this happens it does not allow primitive non flagellate micro life to properly exist on these surfaces.
For a few days the water does not get that to the glass or silicon let alone anything else, the coating allows this to happen.
This shows as a sort of a mucus coating on near everything that is not alive or not moving, thatís the start of compatible surface areas for biological communities, then cycling starts properly.
Then you have patches of bacteriumís and sprawling protists that are there and able to expand quickly if the area allows for this when trouble arises like a death or a bottle of food spilled into the aquarium, now it should be possible to have a massive population boom in minutes to hours if there is room for them and maturity is when a bacterium is able to expand their numbers in the blink of an eye, sort of.
Basically put, you should have as an example only, one meter of surface area with 100 mill of that area consisting of stable diverse bacteria and protists converting your waste with all of the left over area coated where these denitrifying life forms can expand over and cope nicely with what has happened and still no levels of ammonia or nitrite showing in a test.

You cannot rely on a skimmer remaining highly functional always unless you renew impellors at least once a year to be on the safe side and clean the power head impellor area every two weeks!
You can not rely on live rocks surface area remaining as it was, it is supposed to be come covered in corallines and corals because that is what most reefers aim for, let alone the fine algae species that inhabit all aquariums in time like diatoms here and there rendering those spots useless for denitrifying, upon that algae will house denitrifying protists but not bacteria properly.
So for the long term live rock is not reliable for adequate denitrifying!
Plus the internals of live rock over time become permeated with undesirables rendering nitrate reduction weaker as time passes.

Nitrogen cycle.

Organic nitrogen is what a marine aquariums biological filtration is directed at!
When a plant or animal dies or expels waste or aquarium foods are left over, with in this is organic nitrogen and is one of the most abundant elements in the tissues of all organisms.
Amonia to nitrate oxidisers with in the nitrogen cycle are regarded as aerobic,the word means ďwith oxygenĒthat equates to aerobic bacteria being able detoxify oxygen for use in celular respiration.
Aerobic respiration is energy given off by a complex process when O2 and glucose metabolize together inside the cellís mitochondria.

To Ammonia NH3 -aerobic function.
The process of microbial conversion of organic nitrogen into ammonia or ammonium is called decomposition, ammonification or mineralization!
This is applied to anything that was alive and is carried out by many species of bacteria utilizing a bacterial enzyme called nitrogenise.
These bacteria species consist of Azotobacter, Beijerinkia, Clostridium, Desulfovibrio, some Klebsiella, purple sulfur bacteria, purple non sulfur bacteria, green bacteria and also a multitude of symbiotic life forms.
Aquarium hobbyists should be vigilant for potential ammonia because it is the most toxic water-soluble gas, even greater then hydrogen sulfides, which are both naturally produced in aquarium waters.
Ammonia will be ingested by marine life poisoning them very quickly and dissolve gill, eye and over all body tissue. With inverts it destroys their breathing apparatus, eats away at flesh unprotected by body armour as with crustaceans and with corals, renders the symbiotic algae useless and subsequently is expelled causing a bleaching event.
The last and most important adverse affect by organic ammonia is that it gets between the base and the acid that is what we test in aquarium waters as PH, forcing them further apart reducing PH and potentially killing all life as oxygen is becoming toxic!


To Nitrite NO2--aerobic function.
In the primary stage of nitrification, the oxidation of ammonium is performed by many forms bacteria especialy the nitrosomonas species,which equates to the convertion of ammonia to nitrites.
Accesive nitrite levels in parameter trests which equates to any at all,will affect fish more so then any other marine aqquarium life forms.It is a toxin to all life,yet fish respont to its affects quickly from the massive amounts of water marine fish consume each and every day.
Once the nitrites enter the fish and then into the blood stream,the fish is now suffering from what is called brown blood desease and gradualy looses control of its neurological path ways and begins to act and swim very eradic if the parrasites that have noticed its vulnrability donít kill it first.This means the afffected hemogloben can not affectively carry oxygen for the fishes needs and from this the unpleasent lead up to a normally violent death begins.


To Nitrate NO3-aerobic function.
Bacteria which oxidize nitrite (Nitrite-oxidizing bacteria or NOB) also called nitric bacteria. They form a part of the Nitrobacter, Nitrococcus and Nitrospina species.
Bacterial species such as the nitrobacter in the early stages of maturing the aquariums nitrogen cyclers development are responsible for the oxidation of the nitrites into nitrates.As time goes on and full maturity has been achieved,symbiotic protists using bacteria to oxidise nitrite for their own needs and independant protists become the oxidisers of most nitrite to nitrate.
Nitrate in marine aquarium waters.
The elemental nitrates that concern reef or just fish only aquarium keepers are inorganic!
Nitrogen cycle oxidisers take organic matter to inorganic nitrate if a protein skimmer does not remove the organic matter! From there beneficial anaerobes in whatís called the anaerobic zone separate the nitrate atoms leaving pure nitrogen gas.
These atoms that make up the nitrate atom are one of nitrogen and two of oxygen.
Anaerobes in the absence of molecular oxygen, with the exception of the obligate anaerobe, carry out the separation of the nitrate atoms by using the oxygen atoms leaving only pure nitrogen gas.
This is simplistic nitrate separation in a nut shell, a cup of coral rubble left in the aquarium with flow over this will attain a small community of anaerobes after 1 inch into this rubble. You keep this rubble-media clean at all costs and this is the best way to convert nitrate.
A deep sand bed is a very large version of this cup of rubble. Any media like bio balls, cubes and sponges and so on can easily be labelled nitrate factories because they do not comprise of internal areas that can become low to zero oxygen zones!
Algae can be used



To nitrogen-anaerobic function
Anaerobic means a low oxygen environment!
When oxygen is depleted with in a subtrate or live rock,(usualy from nitrite oxidation before these anaerobes),these bacteria first turn to the second-best electron acceptor, which in sea water, is nitrate. Denitrification occurs, and the nitrate oxygen atoms will be consumed rather rapidly leaving pure nitrogen gas.
The bacterium carrying out nitrate atom seperation, though quick, needs a massive area to carry out this function. At least three inches deep of substrate at one and a half times the floor area of the aquarium to give parameter tests results of zero nitrates with out fail. This can work with the combination of base rock in the aquarium and substrate externally kept clean!
The early parts of the anaerobic level or this may become the lower reaches with in substrates and deep with in live rock is labelled anoxic and if anoxic seawater becomes reoxygenized, sulphides will be oxidized to sulfate. Anoxic zone bacteria can with stand oxygen from time to time if in short doses.
After reducing some other minor elements, many forms of anaerobic bacteria will turn to reducing sulfate and are labelled sulfate-reducing bacteria-SRB.
From this action obligate bacteria predominately make hydrogen sulphide, they cannot use oxygen for growth and can be harmed by oxygen and aerotolerant organisms,also oblgate anaerobes cannot use oxygen for growth, but tolerate the presence of it.
If hydrogen sulphide is produced is vast amounts from adverse amounts of organic material entering this area, as it rises and to oxygen rich areas it becomes elemental sulfur. If there are not enough communities of bacteria with the ability to use sulfur, this element will be a short-lived as a toxin in the aquariums waters.
Some largely unicellular anaerobic microbes are protists, but most of the anaerobic microbes are bacteria or archaea.
Anaerobic waters explained-
The term anaerobic is used to indicate the absence of any electron acceptor like mitrate,sulfate or oxygen,plus anaerobic respiration means an energy cycle with less efficiency to produce energy.
At the base of this zone there is usualy hypersalinity deveoping over some time where the obligate anaerobes can increase communities.
Anoxic waters explanied-
Anoxic conditions will occur if the rate of oxidation by oxidisers of organic matter before this bacterium is greater than the supply of dissolved oxygen.
These areas of sea water are depleted of dissolved oxygen.
Anoxic conditions result from several factors; for example,stagnation conditions,density startification ,inputs of organic material, and strong temperature fluctuations.The bacterial production of sulfide starts in the sediments that long term substrates develope, and may expand into the water column.

Hydrogen suphide-
In most cases, oxygen is prevented from reaching the deeper levels by a physical barrier like,hypersalinity,sediment,organic matter or small substrate granual sizes.
(e.g. mud)[1] as well as by a pronounced density stratification, in which, for instance, heavier hypersaline waters rest at the bottom of a basin.

Obligate anaerobe
The producer of hydrogen sulphite in marine aquarium deep sand beds.
An anaerobe that does not require oxygen and lives only in anaerobic environment and can tolerate low oxygen levels.
Exposure to atmospheric levels of oxygen is lethal to obligate anaerobes because they are void of enzymes such as super dismutase and catalase which would convert lethal superoxide forming in their cells due to the presence of oxygen.
These anaerobes will use fermentation or anaerobic respiration.
Instead of the usual oxygen, they use sulfate, nitrate, iron, manganese or carbon monoxide as electron acceptors for their respiration needs.
Obligate anaerobes are bacteroides and clostridium species.
These anaerobes need organic matter entering the bed to accomplish the immensely disrupting production of hydrogen sulphide. This is converted to sulfur with in the water column once it makes contact with atmospheric oxygen.
Life above, upon or with in these beds of media will prevent them from functioning correctly.



Photos of bio media and how they work.
The following photos show where surface area is upon and within the biological media.
Aquarium media is classed as anything non living or non toxic in your aquarium waters like dead coral, bio balls-cubes, sand, gravel, glass, plastics etc.

Once the nitrogen cycle oxidation processes have been applied to the organic matter via aerobic bacteria and protists, any and all substances left over are classed as inorganic.

These inorganic types mainly consist of nitrate, orthophosphate and phosphorus, the combination that is called phosphate.

Nitrate needs anaerobic bacteria, or algae at a rate that is undesirable as it can only achieve minimal conversion and a slower way of absorption called up take or importing.

Either way the algae take in nutrients osmotically through its membrane and utilise or photosynthesis all absorbed nutrients.

These pics are of typical biological media.

A coralline roller that is useful for biological media.



The pic shows it cut open to indicate why it is supreme internally and externally as a form of bio media.



A piece of dried out live rock.



Cut open to show inadequate anaerobic areas with in.



Substrate pros and cons.

This type media bed that works very well for aerobic activities near to the surface and equally anaerobic with in will be looked at as with no floor.

This is best and most affective with a raised floor below.
The gap is to enable more water flow and an area to allow build up of blocking materials below the media and not in it.


Substrate with out a raised floor.
The bottom mark indicates the rising of blocking material in each photo encouraging the oblique anaerobe community to increase over time. These make the potentially damaging hydrogen sulphide.










Bio filtering for reef aquariums, semi natural.

1.The first stage of any external filtering is the removal of as much organic matter as possible from the water as it leaves your tank.

This consists of left over foods, invertebrate and vertebrate life forms faeces and proteins.

The rest consists of dead tissue of either plant life or animal life forms.

This can be done with minimal success as with most hobbyist by the use of a protein skimmer and filter sock.

A skimmer has to be able to break down the bubbles size as it enters the skimmer chamber and the current in the chamber should keep these tiny bubbles in suspension for as long as possible.

While in suspension these particles of organic matter become attached to the membrane of these tiny bubbles similar to pins pushed into a cushion.

Also soluble organic matter becomes part of the bubbles membrane as the bubbles eventually rise up and burst at the surface over and over with the waste organic matter carried up wards and into the skimmers cup.

A filter sock is normally designed for water to fall into it and this way of use subsequently forces some matter through its porus make up and these let through potentially blocking particles of both the organic and inorganic.

The best way to trap and remove organic waste as it leaves the aquarium is to apply a wall of very slight micron size Dacron.

If the waste gets past,it will consist of calcium, phosphorus and discarded plankton and pod shells which is organic silica and calcium carbonate.

Try to get as much of that out as possible because this will account for near all of your bio media blockage out side of the aquarium where anaerobic bacteria exist that processes the nitrate atom made up of one atom of nitrogen and two of oxygen!

Have small pieces of live rock from 30 to 60 millimetres in size on a raised egg crate floor with around a 20 to 40 gap from it to the floor.

The best media is dead coralline chunks, but any small pieces at 30 to 60 mil in diameter of coral will suffice placed on this false floor at three layers deep with the pieces getting smaller as they go up.

On this you sit racemosa caulerpa with a few pieces of the coral chunks weighting the caulerpa dow so it attaches and spreads.

From the coral-calcium where the caulerpa will attach the water can not be any deeper then 6 inches or the caulerpa will become light deficient and will not be able to flourish like most have their refuge set ups.

This area needs lighting for no greater then 20 hours per day and no less the 17 hours per day.

Algae will try to adapt to these conditions and will just falter with the needed photosynthesis and go whatís called, sexual!

So with incorrect needs it is no longer capable of correct photosynthetic functions over some time and of course it goes sexual-dies and your system starts to fail.

Algae does not contain its imported phosphates-phosphorus or nitrate, if these are imported they are converted or used via photosynthesis or cellular up take.

If the algae dies it will go through the nitrite cycle as all dead tissue does and you will get ammonia-nitrite-nitrate-nitrogen and phosphorus.

Never let salinity go below or above 1.025 or below 1.023 if you can help it and never let water temps get above 25c or below 23c for most life forms.

High quality nutrient importing algae begins to malfunction at 25c and above, surge zone taxifolia and chaeto are not high functioning algae forms, though chaeto is a little affective on nitrate

During the 4 to 6 hours of no lighting over the importing algae, the tanks lights need to be on as this area is now mass producing CO2, thatís what algae is supposed to do when there are no lighting colours to activate photosynthesis.

This is the time when a natural calcium reactor is ticking over for the corals under the algae and along from the algae before the CO2 reaches the tank and is off set a little by any algae in there.

This harmless CO2 will decay minute amounts of the calcium releasing strontium, calcium, magnesium, all the components that made up the coral in the first place are going into your water!

Its best to have two algae areas along side each flowing into the other with the centre of the lights on cycle for one as the others lights are off for its 4 to 6 hours.

Lighting has to be over the waters somewhere adding up to 24 hours per day in sections over different areas, thatís a must!

Amongst this algae will flourish immense amounts of plankton, pods and advanced protists, these shed shells and they will block anaerobic areas further along with this type of system or any system with algae present for some time!

Also algae that dies here will add to blockage issues as they are partly comprised of calcium carbonate and that will add to blockages before it breaks down.

A settling pre filter or two will prevent most anything getting the next phase of mostly anaerobic bacteria.
This pre filter barrier has near no waste and food scraps getting to it, so its cleaning can be left until the water level in the pipes is near to overflowing the fail safe holes.

That amount of maintenance is all you need to do, possibly each 5 days or 8 days; it matters not, if it becomes a little bio active it adds up to nothing!

These with high quality algae importing nutrients, can be cleaned under the tap as the algae will import and convert any and all inorganic phosphates that are in tap water and the microbes will handle other substances from the tap water or they just settle out of the water.

Of course if you can use reverse osmosis filtered water, thatís even better!

The next areas should be similar to sand beds.

You can use plastic tubs stacked on top of each other to give multiple beds of coral and shell particles from 4 mill to 12 mill on a floor of egg crate with a 15 to 20 mill gap under it.
The particle beds should be not less then 40 mill deep and no greater then 80 mill deep.
Three plastic tubs with an area of 2-foot by 1-foot gives you an anaerobic and the first 15 mill is aerobic, all up 6 foot by one foot in a 2 foot space.
Multi story layering gives you an enormous amount of bio filtering in a tall and small space.

11.For very good PH control there should be an area of cascaded waters, you can even use a plastic non uv protected house hold rubbish bin for this.
Possibly two foot high by one foot wide and deep is plenty with a drip try on top and then the water exists by bulkheads out the bottom, then this section will help your waters no end.

12.The water is now entering your sump.
Here you have a return pump and a small skimmer that has its flow going onto the drip tray of the cascaded waters to get rid of micro bubbles.

If the area of algae is quite large you do not need a skimmer at all.

The water that is returning to your tank is free of all ammonia-nitrites-nitrates, adverse CO2, organic and inorganic phosphates and toxins.
The waters are now high in calcium-strontium-magnesium-oxygen-amino acids and much, much more!


Fish only marine aquarium.

A fish only marine aquarium can be quite easy to achieve in that fish do not overly need a protein skimmer and with limited waste variations, the biological filter can do its work much more efficiently!

Saltwater fish recycle their urea (pee) to a great degree to cope with living in salt water, so they produce very little protein, again (pee) to cope.

It should be noted that with out a skimmer if you go down the track of keeping corals the waste from fish and any tank life will equate to phosphates, more so inorganic phosphates and this will prevent any success with corals or keeping colours in anemones!

The thing with a fish only tank is to not use live rock for bio filtration at all, that doesnít mean to not have live rock in the aquarium to land scape with and to help take care of some of your bio load, this means to rely on and start your aquarium on a substantial external bio system!

To make your own live rock free of hitch hikers, you need to get some cheap base rock or collect some rubbish live rock and boil it or just put it submersed in hot tap water and than leave it out in the weather for a few weeks after that.

This will kill any life forms on and with in the original rock (dead coral) thatís what live rock is any way, itís dead coral with new life in and on it!

This can now be your live rock in the aquarium to house a basic biological community, though much greater than the commonly used live rock as there is far more surface area on your rock because of no coralline, corals, etc.

Also with in the normal ( live) rock, there are many borrowing life forms that produce substantial protein (pee),all inverts except corals pee a great deal, especially shrimps, worms, crabs and so on.

On fish only tanks (live rock) you need to encourage the growth of algae, some quality caulerpa algae is best, these will take up space on the rock but algae will convert a great deal of your waste gases reducing the load on your biological community anyways.

Corals tend to spend a lot of their time and energy producing some weak or quite strong chemicals and flushing their stomachs if something has upset them, thatís the main spider web look on them at times, their stomach contents excreted as sought of a mucus cross saliva, also if they come out of the water they excrete this including some sun screen materials as a protective screen as well.

Corals can be a nuisance any way, you see over the corals day one coral senses another of a foreign type and it excretes its chemicals (invisible) and so does the other and so on and so on just to annoy each other as a territorial thing and attempt, sometimes at a great distance in the aquarium, to sting each other.

Algae or activated carbons in your sump will remove their chemicals, skimmers remove a little, if it isnít removed the corals of the weaker varieties will stress and die, so fish only with stable PH and a robust bio filter is a good part of the hobby!

Fish and anything else in a marine aquarium need stability, this is best served by not having any covering of your tanks floor or at the most a very shallow covering of calcium grit,(a substrate),this becomes the largest polluter of the aquarium over the long term and even if you use a skimmer, this polluter will surpass what a skimmer can remove and you will need to use activated carbon or reactors at an ever increasing rate!

A substrate in your display tank over time is a slow creeping destabilising mass that takes hold and keeps that success in your aquarium at a far lower level than could have been realised!

Some other life forms you can have successfully with fish and not have to consider them much at all are xenia, shrimps and sponges.

These can add a nice display for a fish tank and not risk your water quality much at all.

Also xenia provides additional algae for the corals internal clades and some sponges are photosynthetic, utilising cyano bacteria with in to help purify your waters.

For a more or less fish only tank, a long with the live rock bio filtering if you want to have this as the main bio filter, try to incorporate a properly pre filtered canister filer if you are not able to add your home made affective sump to make sure there are no traces of ammonia, nitrites and nitrates at any stage.

For the canister filter to work well,it should be totally filled with calcium-based media of substantial surface area (eg,coral rubble,shell grit) these filters never come with proper filtering to be able to insure longevity, add your own filter before waters can get into the canister filter.

Do not open this type of filter once it is set up properly to ensure the bio media is not moved and subsequently reduces its effectiveness and causes PH disruption upon opening it!

To aide in helping PH remain stable, in tank current has to be faced up wards to break the surface of your tanks water to enable co2 in tank to co2 in the room to be in balance, this will help maintain good PH,a small section of cascaded waters will help the PH stability more than any other function!!

All this means is make a trickle filter (sump) and be very concentrated on pre filtering your waters before it gets to it and you really should invest in a chiller, marine life does not like instability, as temp fluctuations will cause these tank life killing events!!

The big question now is, what types of fish are you wanting to keep?



(Filtration areas)

These are for maximum results, not for minimum results for each of these naturally based filter areas.
Live rock, canister filters, shell grit, coral rubble, and all these are filtration areas. †
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Live rock

This was once live acropora corals with new corals, sponges and more growing on it,do not rely on this to carry out the aquariums entire biological filtering, you will regret it eventually or at least have to be very focused.
This filtering is at best small and will diminish a little over time if used on its own.

Pre filter.

This is where you trap waste particles ready for removal every 1 to 3 days, by cleaning it or changing it.
If you go on holidays,its fine for that long once in a while!

Dacron is best for this and at least two slow flow sections of it, some would say use a protein skimmer here, if the skimmer fails at any point,you will have real problems!

No bio filtering works at its best with out the water being pre filtered!!!!!!!!!

This is a barrier of filter wool, Dacron the water passes through filtering out rubbish to be changed a few times per week or wash the rubbish out of it under the tap a few times per week or it becomes bio active (This is pre filtering before the bio filer).


Dry section or cascaded waters

This is the most important part of your filtration in relation to stability.

This area releases ammonia into the air, absorbs oxygen, releases co2,carries out nitrite oxidising plus helps stabilizes ph.

This section is made up of cascaded waters; a waterfall is a dry section, simply put, it is water falling over something and not something actually in the water.

They use to make spinning arms designed around the sewerage system for dry sections, which essentially does the same, waste oxidising, though the spinning arm for sewerage just spreads the waste filled water over the massive wet section!

So dry sections were being used for a hundred years or more.

Its best to make a drip tray and the water that comes through the holes drips over coral,(calcium media is best any where in a marine aquarium)the waters will splash down over it releasing CO2,ammonia and absorb oxygen, this closes the gap between the acid and the base, which is PH and will help greatly to stabilise PH!!

Protein skimmers are supposed to do some of this, but skimmers are designed to coat the bubbles with substances and as they rise and burst, to remove it, which renders its gas exchange only slight, not extensive like a dry section!


Wet section
Your live rock is the wet section in a live rock biofiltered aquarium though it is unreliable!
This area externally can be small but needs to be long sp time used for oxidation processes and parasite reduction, have some externally even when live rock is present in your aquarium as well.

Long means if you put it in a pvc pipe and run the water through it that way, make it two feet long not one feet long.

This is a section of shell grit, coral rubble, what ever calcium based with lots of surface area in the water somewhere, like an under gravel but better and not the dirty under gravels used by most!

Live rock is a wet section, but slightly ineffective, not enough surface area over time or for situations that arise!
A wet section, its your most important denitrifying bio media and it has to be always in the water and all your water has to pass through it or over it slowly and have it very long and extensive if possible!


Plenum or deep sand bed.
A plenum is basically a very clean stagnant (dead spot) section that houses anaerobic bacteria to convert nitrate to nitrogen.
Try to imagine an under gravel filter switched off!!
This area is essential for nitrate reduction, beyond what the live rock is supposed to handle.
This can be made with any small particles from 3 to 8 mill in size and can be shell grit-coral rubble or white marble.
All you need is perfectly pre filtered water moving over it and it will achieve your nitrate reduction nicely.

Refugium.
This area is based on algae these days, sadly with a substrate!
A refugium was for a (refuge) for many forms of life.
The algae in here should be racemosa caulerpa,some surge zone taxifolia caulerpa and any others you can add.
The water depth, from attachments to the waters surface should be no deeper then 6 inches and fluro replacement tubes LED lighting left on for no greater then 20 hours and no less then 18 hours per day.
If large enough and shallow enough with the right species of algae, like caulerpa and turtle weed etc,with no fine substrate, it will convert phosphate, nitrate, co2, pretty much all impurities in your water to some valued elements for corals as such and if handled correctly and set up properly, this is a god send to your aquariums stability.

Protein skimmer
A skimmer will remove some organic waste before it becomes part of the nitrite cycle and you than won't need that extra amount of bio community to oxidise it.
It should be remembered that once a skimmer is in use before an external bio filter, it cannot be left off by choice or by accident, the waste it removes will now need a large enough biological community to convert the extra that needs oxidising!

If this community has not been matured and surface areas with in your bio area are not robust enough to increase in size to accommodate this extra load when your skimmer is off, than you now have problems with PH from toxic ammonia and fish killing nitrites!


In tank current

There should be a reasonable even current over your live rock as it does a lot of ammonia, nitrite, nitrate converting, gas exchange and the food dispersion is important as well.

The old school style of filtering supposedly produced excess nitrates, or the term, nitrate factory was used for them, this was a result of pore pre filtering and maximizing aerobic to anaerobic areas that became clogged.

They actually produced some serious gases from the wrong kinds of bacteria, like an aged deep sand bed would, not excess nitrate and not because they did not work, just pore design!

You cannot have too much settling style pre filtered external bio filtration, only to little.

If you donít prefilter, success will be lost over time.
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