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Hi there,

One of the most important subjects known to man……filtration.When it comes to filtration most people can feel a little overwhelmed by the concept.Not to worry that’s why i am gonna try in a few words to make it real and easy for you.On the basis that some of you have read some of my blogs then you should know that water quality is the key issue for fish keeping.In order to maintain our water quality we do a weekly test with our test kit don’t we folks?…..yes we do Ian….okay that’s cool.Remember your test kit answers your questions before i do.On the basis that our water quality (not Clarity) is up to scratch then the next thing will be the control of solids and all the particulate matter we see in our aquariums.

It is those annoying floating suspended bits that freak us out the most is it not?It does not matter what fish you keep it is always the same.I come across this all the time.Well managing physical waste is called mechanical filtration as opposed to biological filtration.Biological filtration is the action of the bacteria we culture in our filters….it can take up to two months to colonize our filters properly with nitrosomonas  and nitrobacter the two bacteria that form a biofilm in our filters…this is what we call the biological function of our filter.It is an easy concept to understand.These bacteria are slow growing and are oxygen dependent they have an optimum temperature for growth over the temperature we keep our fish at so technically our filters never run to their optimum levels….but that’s by the by.On the basis that they do for argument sake the populations of the colonies can only grow in accordance with the amount of food that is available to them…..this food source is Ammonia.Most of this chemical is produced by the exchange of gases through the respiratory function of the gills.But i am getting off on a tangent here as i do……the biological function of our filter must be safe guarded at all times.

It takes very little to damage this unseen part to our filter.I will explain this in this way.When you are cleaning the sponges in your filter obviously using aquarium water to do so have you ever noticed the slimy feel to the sponge.That is the jelly or bio film i am talking about.Have you ever noticed that no dirt comes out till you squeeze the sponge several times then whoooosh the water is filthy….that is you sloughing off this bio film.Once you do this you compromise everything this is why i suggest using two filters and alternate the cleaning of them.Most people will have problems after a cleaning session.Your fish will still produce the same amount of waste but your filter is biologically dead.If your ammonia levels rise on your test kit then this has happened.I always suggest regularly testing after maintenance to keep an eye out for a spike in the levels.

Once you turn your filter off for more than an hour you can be sure this will kill your biological function too.Low oxygen levels are another sure way to mess up filter performance.Filters need as much oxygen as your fish do.And remember oxygen is temperature dependent.The higher the temp the lower the amount of available oxygen.The third type of filtration we use is chemical.Without going to deep into this because i want to make this simple is the use of chemicals or products that interact with your water in an unbiological way like using resins to absorb Nitrate or else blockers or agents that detoxify.

If we choose and use the correct filter we should have very little issues with our aquarium.Remember a filter is an inert dead thing until you fill it with invisible life.Your filter is not a wonder machine….forget the shiny knobs that is all sales pitch.Bacteria will colonize and settle on any surface as long as there is suitable food source and oxygen levels so you can make a filter using your underpants if you want.What i look for in a filter is quite different.I look for media capacity.I look for through put ie turnover.If you want to nitpick i would test the oxygen levels at the input stage then again at the out put stage to see the amount used in biological function but this is only for my interest really overall oxygen levels of 80 percent should be enough to carry the tank.My suggestion is get a good external for one.I love externals that’s is why there are so many on our site and we sell them so cheap.They take up very little room in the tank which is pleasing to the eye.They have a very high carrying capacity and if you use heterotrophic cultures of bacteria in your tank on a weekly basis you should be able to reduce the physical load in your system by up to 70 percent….imagine that.Yes we can do this.We have done it for Maynooth fisheries.We reduced waste levels by a dramatic amount riding the lake of blanketweed into the bargain.So if we can tackle a lake imagine what we can do to an aquarium.For aquariums you will see similar products title sludge busters etc. I suggest you use them but they have to be used regularly for the results to really shine.

Anyway this discussion is a quick blog to help some of the confusion when it comes to selecting filters.Most filters are good.There i said it.Choose one that suits your needs.That is where we come in.Go to your local fish shop and have a chat….biological filtration is my life i have over 40 sump filters alone to manage in work….if you have any queries i would be delighted to help out.


Ian Patrick Compton