Brief Introduction on Filtration

By Frank G Anderson

My first contribution to this on-line magazine was last month, and covered maintenance of an undergravel filter. I had one reader vehemently in disagreement with much of the article's content, and while giving him credit for being open and honest in his criticism, can not ignore the fact that his comments reflected one of the hobby's fears - that of breaking down a filter system. That said, even before filtration systems should be examined for breakdown, maintenance, or replacement, they must be first assessed before they are even bought.

Filtration is one of the most vital elements in successful aquarium keeping. Without proper filters, sized correctly, and maintained regularly, several things can go wrong in the aquarium, and this imbalance will always be passed on to the fish to their detriment. This month's article is related to a brief explanation of filtration, and describes some of the more basic filtration units and how they should be used. A note: many hobbyists will insist on more sophisticated filtration systems, but the old rule about simplicity still survives, alive and well. Which is how we want to keep our fish. I personally feel that without some background in the basics of filtration, and without personal efforts in regular filter maintenance, all the sophistication in the world won't save your fish.

Filtration is meant to improve water conditions, or to stabilize them, or to produce water conditions that are ideal for your fish and plants. Why is it necessary to improve water conditions? Because water for most aquariums comes from the tap, sometimes directly from tap to tank. This is not the ideal method of placing water in your aquarium, but it does happen. Water from the tap is first and foremost usually chlorinated, and chlorine is harmful, in higher concentrations, to fish. So a holding tank can be set aside for tap water to dechlorinate itself over a 24-hour period. But thats not all that is "wrong" with tap water. There's hardness to consider, total hardness and carbonate hardness. How many parts per million of dissolved solids are there? And what about pH? Does the tap water come out with a high (over 7) pH or a low (under 6) pH? And either way, what can be done about it? Temperature is another consideration. If water is introduced to the tank that is too hot or too cold, it can have harmful effects on fish and plants, and bacteria colonies.

OK, is there anything else? Yes. Inside the aquarium. Inside the aquarium, something called a biological cycle establishes itself, or gets established. Basically a balance between beneficial bacteria, wastes generated by the fish and total aquarium system, and water changes made by the hobbyist, the biological cycle is supposed to stabilize toxic levels of nitrites, ammonia, etc., in the tank and with the aid of regular partial water changes, results in water quality that is healthy for your fish and plants, even healthy enough for fish to breed in and to raise young offspring. The filtration process is a vital element in this biological cycle. Whatever materials you have in your aquarium, whatever types of filters you use, whenever you forget to properly clean filter media, or when you neglect to use the correct kind of media for particular filtration needs, that biological cycle willbecome unbalanced, and throw toxic materials back into the aquarium where they will contribute to fish parasite and bacterial growth, fungus and other water-related stresses that can and do lead to fish deaths. So filtration is vital. Filtration maintenance is equally vital. And filtration types can be, well, confusing. What kind of filter to choose, when to change, how large should it be, etc.?

I personally opt for overdesign in most filtration steps I take. Not overdesign to the extent that the fish will suffer, but overdesign so that the filter equipment will operate at maximum load at no more than about 75% capacity. This reduces the wear and tear on the filter, and makes it a longer-lasting contribution to filtration. It helps to compensate for occasional forgetfulness in maintenance, and helps act as a buffer for the occasional failure in other filtration in the aquarium. Which brings us to. "What? What other filtration in the aquarium? Isn't one filter enough?" The answer is almost always "No." One filter is usually not enough. Filter failure, and as mentioned all ready, lack of maintenance, and imbalances that are not expected, can lead to virtual failure in the ability of any single filter, let alone all of them, to effectively protect and promote water quality.

That said, which filter is best? My preference is the undergravel filter. It is economical, simple to install, and easy to maintain. It can be augmented with above filter plate sponge layers, and kept in great shape by simple monthly siphoning. One reader of last month's column queried me about the BioWheel versus UG filter. Which one did I think was best? My reply was and still is that both are good filters, but that the undergravel filter is probably the winner all-round because of its price and little requirement for maintenance, and the fact that it uses, I believe, less energy than the BioWheel. I could be mistaken on this point, and if anyone has real evidence to the contrary, please let me know. The BioWheel, though, is a good filter. It is one off-take of the tank-mounted box filter, and uses a rotating wheel with filter media to cultivate aeration and bacterial processing of water. It might be termed a hybrid between a wet/dry filter and sponge filter in a theoretical sense. Again, selection depends on tank size as well as other factors. A 10 gallon tank would be rather small for a BioWheel as a fifty-five gallon tank would be somewhat large for a BioWheel to handle on its own. When you get over thirty gallons, the BioWheel, I feel, should be augmented by at least an undergravel filter if you don't already have one installed.

Perhaps the simplest combination of filters for beginners and for hobbyists in general who enjoy simplicity is to opt for an undergravel filter and sponge filters, perhaps with a BioWheel thrown in for good measure. All these will help keep in-tank conditions prime, but wont keep water conditions from eventual deterioration. Thats where water changes come into the picture, and they will be discussed before the close of this article. But back to filter types. Sponge filters are usually air-driven, as they "suck in" water from the tank, through the sponge, and up and out through an effluent pipe that hopefully adds to water surface motion which is where the water/air oxygen exchange occurs. Sponge filters are notoriously underdesigned, in my opinion, because they are often seen to be horribly crammed with dirt and evenblack with sediment. When sponge filters get to the point where they are in this condition, you can be certain that water conditions in your tank are amiss to some extent. Anyone who has had filters in this condition, then cleaned and replaced them, has noticed how much better and active the fish in the aquarium appear. They enjoy good water conditions.

Hobbyists also use polishing filters, or external usually cannister filters, to polish or brush up their water conditions. These filters are run by their own motor, and have an influent line that draws water from your aquarium into the filter compartment, where it is forced through a membrane or other media, and then back into your tank. The so-called polishing description came about because its similar to polishing a car, getting the dust off and making things look better. Not only will your water look clearer when run through these filters, but it will be cleaner, with much of the water-born sediments and even floating worms, etc., filtered out. Recommended frequency for this kind of filtration? Perhaps once a month.

I am leaving out the wet/dry and trickle filter systems in this article, as they will be covered later. But if any readers wish to ask questions, or offer comments, I would be more than happy to reply or consider them for comment. If you don't mind having your letter printed in a follow-up article, please provide a no-objection with your comments and/or questions.

Finally, water changes.

The aquarium is not like the ocean, or stream bed that gets virtually new water all the time. It is a much more closed system, and accumulates waste, even with filtration. After all, even the worlds oceans and streambeds become polluted, indicating that the so-called unending sources of new water are not really unending. The situation is vastly accelerated in aquariums. They are closed systems, unless an extensive outside filtration system augments or takes care of all water conditioning. So, water changes are necessary for aquariums. How much and how often? Shakespeare could not have posed any more intellectually-posing a question. It depends is the answer. But for regular safeguarding of your aquarium water, regular water changes usually involve some 20% a week. For overpopulated tanks, for aquariums that are overloaded or under-maintained, the maintenance and water changing frequency should be increased. Which puts some strain on your back up water reserves. It pays to be prepared by preparing first, and staying with a simple yet regular maintenance regimen.

Hopefully, this does not sound too complicated. It isn't, and just an hour a week can make all the difference to your and your fish.