CHEMICAL FILTRATION:

  As the natural processes in the tank take place, other waste byproducts can build up. For example, most dry fish food contains colored dyes to make the product appear more appetizing. (Whether it's to make the product appear to be more appetizing to the fish or to the fishkeeper is another topic.) At any rate, all those pretty red, yellow and bright green flakes are probably treated with dyes to make them appear colorful. These dyes slowly build up in a tank. Over months, with the addition of new fish food every day, the tank's water may eventually begin to take on a noticeable tinge of color. Decaying plant waste is another source of unwanted color. Other unwanted byproducts of the aquarium's natural processes might result in unwanted odors, such as a "fishy" or "musty" odor. Finally, there are quite a few organic waste byproducts dissolved in the water that may or may not be removed by biological or mechanical filtration. To remove these dissolved organic compounds, one can either dilute them out with weekly water changes (best), or one can use Granular Activated Carbon (GAC). This is the black stuff commonly sold in boxes in aquarium stores. It is also found sandwiched inside some filter cartridges, such as those found in Emperor, Penguin, or AquaTech filters. In some filters (such as the AquaMaster or AquaClear filters), filter carbon is provided in separate bags or filter layers, so that the knowledgeable aquarist can make his/her own decision about whether to run carbon or not.

  There are arguments for and against carbon, and each side slings "scientific studies" around as a weapon to prove their viewpoint is correct, while the other side is depicted as nothing but a bunch of slavering imbeciles who know nothing about fishkeeping. Of course, the truth lies somewhere in the middle.

  Advantages of running carbon include removal of unwanted colors (usually yellow), unwanted odors, and removal of other miscellaneous organic waste products. Carbon also removes chloramine (overnight), but only when the carbon is new (less than 48 hours old). Still, this can be an advantage if your tapwater contains chloramine. Carbon does have a finite life, depending on how much organic waste is in the tank's water. Carbon can adsorb only so much chemical waste, and after that it just becomes an inert surface upon which (if left in long enough), bacteria may grow. Some aquarists take advantage of this fact. Since carbon provides a relatively huge surface area for bacteria, some aquarists deliberately run the same carbon for months or years. Bacteria colonize the old carbon and provide another large surface area for biological filtration. Occasionally one runs across the argument that if left in too long, carbon eventually releases its bound-up toxins. If this were true, then that means we could rejuvenate old carbon simply by putting it in water and letting it sit for a few months, after which the carbon would be cleaned of organic wastes and ready to be put back in the tank for further chemical filtration. Obviously, this does not occur. Carbon cannot be rejuvenated (unless you happen to keep a blast furnace in your spare bedroom). If you want to run GAC, you'll need to replace it every 3-4 weeks, because it will be pretty well saturated with chemical waste material by that time.

  Disadvantages of running carbon are few, but worthy of consideration. Some scientific studies have suggested that carbon removes "heavy metals," which can include Iron and Manganese, essential to plant growth. If your goal is to have healthy, vibrant plant growth, then it's probably best not to run carbon in your filter. If you have plastic plants, this is not a consideration, and carbon should certainly be an option for your tank.

  Not insignificant is the cost of GAC. Several well documented studies have shown that some carbons are better than other carbons. In general, carbon made from coconut is not as efficient as carbon made from bituminous coal. If you are going to run carbon, it would probably be best to run carbon from coal, such as Aquarium Pharmaceuticals carbon, or that marketed by Marineland under the Black Diamond label. Unfortunately, this carbon can be rather costly, and needs to be replaced every 3-4 weeks, increasing the cost of running your tank(s) over a year's time by a considerable amount.

  Is carbon really necessary? Definitely not. When you do your weekly water changes (you are changing your water faithfully every week… right?), you also remove anything that can be removed by carbon. Thus, over a year's time, waste byproducts are constantly being discarded every time you do your water changes. Carbon, then, becomes an expensive option. And it IS an option, and not mandatory.

  Suppose you have decided you really don't want to run carbon in your filter because you have also heard that plants do better in tanks free of carbon? You need to take this into consideration when choosing a filter. Some filters are quite simple to run without carbon. The AquaClear, AquaMaster, and Whisper filters are easy to run without carbon. So are canister filters, such as the Eheim or Fluval. Other filters (such as the Emperor, Penguin, or Regent/AquaTech) force you to run carbon whether you want to or not, since it's sealed in the filter cartridge and cannot be removed easily.

  Other considerations to ponder when choosing the filter for your tank would include making a decision between different physical types of filters.

Corner Filters:

  Also known as Box Filters, these are the old favorites that started aquarium filtration. They consist of an economical little plastic box designed to hold a significant amount of filter media of your choice. Water is pulled through the box by way of a bubbling airstone. The water passes through the filter media and is cleansed. Although the technology is old, these filters still carry some significant advantages over other means of filtration. For one, they are very economical. Corner filters (such as the Lee Triple Flow Corner Filter) sell for less than $5. The Lee filters come in 3 sizes: Small (good for about a 10 gallon tank), Medium (20 gallon tank), and Large (30 gallons or larger). Several such filters can be run in larger tanks. Thus, a pair of Large corner filters will handle the waste load of a moderately stocked 55 gallon tank.

  Media for these filters can be anything you want. The "traditional" method is to run about 1" of GAC in the bottom of the filter box, overlaid with filter floss. This provides excellent mechanical and chemical filtration.

  Biological filtration is not usually well performed by these filters, but as discussed above, biological filtration is very easily attained just from the tank's glass walls and ornaments, with no help from the filter.

  A disadvantage of corner filters is that they do require regular servicing. This involved pulling the box to the surface, carrying it to the sink, discarding the carbon and filter floss, and refilling with fresh media. Then, the box is replaced in the tank. This is no insurmountable chore, but it will involve getting your hands wet.

  Other media combinations that will work well with a corner filter would include to fill the box about half-way with Eheim's Ehfisubstrat or Seachem Matrix. These sintered glass materials WILL provide huge biological surface areas that CAN biologically filter the largest of tanks with ease. An overlay of filter floss will perform mechanical filtration and keep the sintered glass material from becoming clogged with debris.

  Your imagination can create other filter media combinations. All filter floss is an option. Or, you might consider cutting some filter pads from bulk and filling the compartment, for superior mechanical filtration. You might also consider keeping a corner filter on hand for the special occasions when you need a particular media. For example, if you don't normally run carbon, but you wanted to quickly remove unwanted medications or colors from that new piece of driftwood you added recently, then you could fill the corner filter with carbon and quickly remove unwanted chemicals.

  I think the box filter is vastly superior to all other filters in fry tanks. Since the suction through the filter is very gentle, fry are not likely to be pulled into the filter box. However, if they are, they will simply land on a soft pillow of filter floss, where they can swim until they find their way out, or until you "rescue" them. Power filters and canister filters can easily kill fry, by grinding them up in their impeller blades. To render power filters "safe" for fry, sponge filters must be placed over filter inlets, but this reduces mechanical filtration. Also, sponges cost about the same as a corner filter. A little thought will quickly show you that the corner filter is THE choice of filters for fry tanks, most particularly in tanks where the fry are microscopic (such as Rainbowfish or Corys).

  Another disadvantage of the box filter is that it must fit inside the tank, taking up space. However, they enjoy one advantage found in no other filter: they are relatively immune to power failures. During power failures, and bacteria in the box will not die because they will be exposed to aerated aquarium water, and cannot develop anaerobic growth as can other types of filters (most notoriously, the fluidized bed filter suffers from this defect). When power is restored, the corner filter continues bubbling away as if nothing had happened. If you live in an area where power failures are frequent, you might find the corner filter is the answer to your prayers.

Power Filters:

  The work horses of the aquarium industry. These are boxes that hold the filter media in the water flow, either by forming filter floss into a cartridge, or by providing a large box enclosure to hold the filter media. Water is pulled by force into the power filter by way of a small electric water pump. The dirty water is then pulled through the media, and dumped back out into the tank. Some (such as the AquaClear and Supreme line of power filters) provide room for very large amounts of media. Indeed, the AquaClear and Supreme filters approach canister filters in media capacity. Other power filters, such as the Whisper or Penguin, provide convenient filter cartridges overlaid with relatively small amounts of filter floss. These cartridges are a snap to change: simply pull the old cartridge out, and slide in a new cartridge. Remember, the bacteria lost this way are minimal since filters don't provide all that much biological filtration in the first place, and the relatively short time the cartridge resides in the filter box does not permit full colonization by bacteria. (It takes about 4 weeks for any filter media to become colonized so that it performs biological filtration.) While convenient, this convenience comes at a price. The filter cartridges cost around $3 apiece. If you change these cartridges on a weekly basis, that means the cost of operating your cartridge filter jumps to around $150 per year! For that amount of money, a much better filter can be purchased.

  The AquaClear filters combine the best of corner filters with the best of power filters. They are capacious, holding large amounts of media. The media can be customized so that you can run - or not run - anything you choose. Since you can choose washable media (sponges, etc.) in theAquaClear, the cost of a year's operation of the AquaClear can be reduce to… zero. Another distinct advantage of the AquaClear filters is that the motors are detachable and replaceable. Thus, in the unlikely event that you should experience a motor failure (a very rare event), you can replace the motor on the AquaClear filter. You cannot do this with the Emperor, the Penguin or the AquaTech filters. Motors are also replaceable on the Whisper and AquaMaster filters.

  Some filters offer flow rate controls; others do not. Flow rate is controllable on the Emperor, the AquaClear, and the Whisper filters. Flow rate is not controllable with the Regent/AquaTech, the AquaMaster, the Penguin, nor any canister filter.

  When choosing any power filter… or for that matter, any filter of any type… it's best to choose a filter rated for a larger tank than you are running. Filter manufacturers seem to rate their filters very optimistically. That is, they rate them for very large tanks that would be possible only if you were performing very frequent maintenance on the filter. While it is theoretically possible to filter a 55 gallon tank with an AquaClear Mini or a Penguin 110, this would be possible only if you cleaned the filter every few days. In general, I like to run a single filter on my tanks, with the filter overrated by about 100%. In other words, if the filter says it's rated for a 20 gallon tank, then I consider that to be a good filter for a 10 gallon tank. If the filter says it's rated for 55 or 60 gallons, I won't run it on anything larger than a 29 or 30 gallon tank. Thus, for example, the AquaClear Mini makes a good filter for a 5 gallon tank, the AquaClear 150 becomes a great filter for a 10 gallon tank, the AquaClear 200 makes a great 15 or perhaps 20 gallon tank filter, the AquaClear 300 is a perfect match for a 29 gallon tank, etc. The AquaClear 500 is a very over-engineered filter, and is an exceptional filter for large tanks. It holds 4.2 liters of media, as much as a medium sized canister filter. The 500 can easily handle the needs of a 55-75 gallon tank, and can handle a much larger tank (200 gallons or more) if it is maintained on a regular basis. For very large tanks (300 gallons or more), filtration needs can be met with a pair of AquaClear 500 filters.

  Filter media in the AquaClear can be customized to be anything you wish. Factory recommended layering of sponge overlaid by carbon will do an adequate job, but greatly improved filtration can be achieved with these filters by putting a single sponge in the bottom of the box, overlaid with about 1" of filter floss, and topped off with a sintered glass media such as Siporax or BioMax. An AquaClear filter arranged in this matter is simply the best power filter available. The sintered glass provides an enormous surface area for bacterial growth, and shifts much of the biological filtration from the tank to the sintered glass. AquaClear filters are very good at restarting themselves after power failures, and are not harmed by power outages.

(Note: permission to copy is required)

(This article has been contributed by one of the users of this website. The webmaster does not own the contents of this articles and is not responsible for the correctness of the contents. The user shall decide if this is correct and if any information is wrong please write to the forum. Other articles on the same subject are welcome and will be included in the same page with the authors name)