Filters and filtration
In this article I'll be discussing the most commonly used filtration media and the types of filtration that occur in the aquarium.
Why is filtration important? Filtration removes from the water column solid and dissolved waste products that would otherwise pollute the water, and subsequently cause stress and illness in your fish.
Most methods of filtration also cause water movement and currents that are beneficial to fish and plants as it stops the water from stagnating.
Before we get into the filter media a word of warning about wonder products - in life as whole there are no true shortcuts, all you do is save up the corners until you have a big pile that falls on top of you. You may think that is off the point but let me draw your attention to products like ammo-carb, ammo-rocks, nitra-zorb et al, and any products containing zeolite.
Although these work exactly as described (removing ammonia and/or nitrogenous waste products) they are the weak link in any tank. The previously mentioned products have a finite life span and must be replaced or recharged regularly - during this time their effectiveness is reduced and as such nitrogenous compounds can build up to dangerous levels. These products literally starve nitrifying bacteria and so leave an aquarium without a biological filter in the event of their failure - fish illness and deaths soon follow as ammonia and nitrite levels rise.
Mechanical Filtration
This type of filtration traps large particles like fish waste and uneaten food, removing it from the water column. Effective mechanical filters will make a tank look clean by ensuring that the water is not clouded by suspended particles. A clean looking aquarium does not mean that you have a clean aquarium however, it just means that waste is out of sight.
Care:
Mechanical filters require regular cleaning in order to work efficiently. If they become blocked with waste products oxygenated water cannot flow through and it's possible that the filter would become anoxic, which would in turn release ammonia, nitrite and other highly toxic N-compounds. The most common mechanical filter found in freshwater tanks is the Under Gravel Filter (UGF) and Internal Power Filters(IPF). The UGF demands regular, thorough gravel cleanings to ensure that it does not become blocked (something that is difficult to detect), while IPFs require cleaning the filter (if this is acting as a biological filter as well, then the cleaning must be done in tank water).
Biological filtration
Biological filtration employs bacteria to break down waste products into less harmful compounds. The bacteria generally responsible for this are called nitrifying bacteria and convert ammonia into nitrite and further into the less toxic nitrate. Nitrifying bacteria live on the surfaces within the aquarium - the substrate, plants and decorations and on filter material. It is important to ensure that biological filter medium does not come into contact with antibiotic agents including chlorinated water.
Care:
As already mentioned, great care must be taken to ensure that your biological filter does not come into contact with antibiotics or antibacterial agents. The biological filter comprises of bacteria and the afore mentioned substances do not differentiate between good bacteria (nitrifying) and bad bacteria (pathogens). If there is a sick fish in your aquarium whenever possible try not to medicate the whole tank, or whenever possible use nothing more than salt as your medicine. In the event of your biological filter being a sponge or floss power filter or UGF it is essential that the water flow is continuous. If the water flow is interrupted for an extended period of time the bacteria will suffocate and die.
Chemical filtration
The
most common chemical filtration medium is activated carbon. The need
for a chemical filter in the freshwater aquarium is debatable and there
are proponents and opponents. Personally it is not something that is
a permanent feature in my aquarium but does have its uses.
Chemical filtration removes things like metal salts, humic acids and
medicines, it won't remove nitrogenous compounds. It's great for keeping
the aquarium water crystal clear. It does have a finite lifespan however,
it can only absorb so much and once it is saturated it no longer functions
and is useless, requiring replacement.
Care:
The only care is ensuring that it is replaced before it becomes depleted and useless.
Natural filtration
Before all these new fangled power filters and such the only method of filtration available to aquarists was in the form of photosynthetic plants (for those who could successfully grow them) and algae. Actively cultivating algae for filtration is something peculiar to Europe, very few Americans seem to appreciate the benefits of the dreaded algae (for one, anyone can grow algae!). Plants use N-compounds as a food source and oxygenate the water throughout the day, they also provide extra surface area for nitrifying bacteria.
Care:
As long as light and nutritional requirements are met little care is needed except possible pruning. You should always familiarise yourself with the plants that you intend to grow to ensure that you will be able to successfully cultivate them.
What filtration?
Ideally your aquarium should have as a minimum biological and mechanical filtration, however in a lightly stocked, heavily planted tank mechanical filtration may not be required.
There is no such thing as over filtration - colonies of nitrifying bacteria are only present in sufficient quantities to deal with the bioload. The only problem that may be encountered is that of too much current. If fish have to constantly battle against a current with no respite they will become stressed.
This article and the text contained within are ©David Nicol 2001 - All rights reserved. Permission is granted for distribution of article for personal use only.