Emperor filters are the best cartridge filters made today, and would be your best choice, second only to the AquaClear filters. Emperor filters are sturdy, and their motors are powerful and reliable. The motors are not replaceable, but fortunately motor failure is a rare event. The Emperor filter cartridges are very sturdy, providing a plastic frame that holds a spoonful of GAC, and overlaid with a ½" layer of filter floss. This filter cartridge actually provides very little filter media, but the Emperor provides a second "accessory" filter cartridge that can be filled with whatever you desire. It may be filled with filter floss (for additional mechanical filtration), or carbon. The box conveniently holds 56 Siporax or BioMax rings, for vastly improved biological filtration capabilities. The Emperor 400 provides two floss filter cartridges and two accessory cartridges. You may run carbon in one accessory cartridge, and BioMax in the other, or specialty filter media of your choice.

  The Emperor is generally good at restarting itself after a power failure, and is not harmed by power outages.

  The biowheel provides additional biological filtration, although I fear that much of the biowheel's performance is the product of an advertising writer's fertile imagination and not the result of scientific testing. Simply put, since biological filtration is easy to attain with no filter at all, the biowheel does not "herd" all the bacteria onto itself and perform all the fantastic biological filtration claimed in its advertisements. Bacteria will still grow throughout the tank, and the biowheel becomes just another surface to support the growth of bacteria. It is by no means the ONLY biological surface in the tank or filter. Any filter can easily maintain ammonia and nitrite levels at zero, and it doesn't get any better than this. Thus, biowheels don't perform biological filtration any better than another filter. All of them reduce ammonia and nitrite to zero, and no lower.

  A distinct disadvantage of the biowheel is that it aerates the water, driving off all excess CO2 and causing a pH shift in the upward direction. If you don't keep plants, this may be acceptable (but not if you raise acid-loving fish such as Tetras, Discus, Angelfish, or Corys). However, planted tanks would be well served by a filter other than one running a biowheel, since plants need the excess CO2 to grow. You can get the best of both worlds by running an Emperor filter minus the biowheel on a planted tank. If biological filtration is an issue with you, consider running the Emperor filter with a Cellpore cartridge in place of the accessory basket. The Cellpore cartridge is a "glass/ceramic foam" material that provides thousands of square feet of extra surface area for the growth of bacteria, more than making up for the lost biowheel.

  Penguins are just lightweight versions of the Emperor. If one is considering a Penguin, the money would be better served getting an Emperor filter, which has much greater capabilities.

  AquaMaster filters are interesting filters. They provide high rates of water flow, more than most other filters. However, these high rates of water flow come at the expense of media capability. While the filter boxes are capacious and would seem to invite being filled with accessory filter material, the fact is that any restriction of water flow from extra media quickly results in water bypass, i.e., water overflowing around the water intake tube. The filter "cartridge" consists of a plastic frame that holds two thin layers of filter material, one polyester floss and one carbon-impregnated floss. These filter media are easily replaceable, but do not invite easy customization beyond including the carbon or leaving it out. One way to improve performance of the AquaMaster is to run a sintered glass (or glass/ceramic foam) cartridge as supplied by Cellpore. Unfortunately, the AquaMaster design does not provide an extra slot to hold filter cartridges (as does the Emperor), so the Cellpore cartridge must be gently wedged into the filter box, preceded of course by the filter floss cartridge. Water bypass is inevitable, although it's a small amount of bypass and is probably insignificant. Still, Supreme could improve the mechanical design of their AquaMaster filters and bring them up to date by providing an extra slot for Cellpore or other accessory cartridges. A flow control to reduce water flow would also be a great improvement for these filters, and would allow the large filter media box to be packed with useful media. One frequently unnoticed advantage of the AquaMaster filter is that it has a little airline tube that allows air to be mixed into the water for superior aeration. While this is of no interest to me (I consider any power filter to adequately stir the water for adequate aeration), it does provide an intake line for the addition of supplemental CO2. Thus, the AquaMaster is probably the "sleeper" filter for planted tanks: carbon can be removed, and CO2 can easily be fed into the water column without cumbersome home-made CO2 distribution methods. Still, its brisk rate of water flow is a disadvantage and needs to be addressed by the manufacturer before this filter catches on. The motor is replaceable, an advantage.

  Supreme, the makers of the AquaMaster filters, do make a "thin" version, the AquaMaster models 100 and 150. These filters are the perfect answer to the aquarist faced with very limited space at the rear of the tank. Their slim profile allows them to be used in spaces where no other power filter will fit.

  Regent/AquaTech filters are actually made by Marineland, the makers of Emperor and Penguin filters. Indeed, Penguin filter cartridges will fit perfectly in the AquaTech filter, and vice-versa. AquaTech filters are very competent "vanilla flavored" filters, the Chevrolets of the world of filters. They provide no flow control (a disadvantage), and do not come with biowheels (an advantage for the keeper of planted tanks). The motor is an integral part of the filter, which means that in the rare event of a motor failure, you are left with no choice but to replace the filter in its entirety. Still, filtration is quite adequate, and will give years of good performance.

  The operating cost of all cartridge filters such as those used by the Emperor, the Penguin or the AquaTech, can be significantly reduced by cleaning and re-using the filter cartridges. This is easily accomplished by simply taking the old, dirty cartridge out to the patio and giving it a blast of water from the garden hose. In seconds, all debris is dislodged and washed away, leaving the cartridge as good as new to perform mechanical filtration. Of course, the carbon inside the filter will not be rejuvenated in this way, and after one or two uses becomes inert. This is not necessarily a disadvantage since, as discussed above, water changes will remove anything removed by carbon. Thus, rinsed cartridge filters perform good mechanical filtration, while the carbon simply becomes (with time) just another biological surface.

  Whisper filters are well made filters, and have probably the best flow rate control found anywhere. Flow rate can be adjusted from full flow to zero, or anything in between. The filter cartridges consist of little floss bags that can hold carbon or any other filter media of your choice. As with the Emperors or the Penguins, the filter floss material can be rinsed clean and re-used. Newer Whisper filters also provide a sponge that provides a good biological surface area to hold large amounts of beneficial bacteria. You can also substitute a Cellpore cartridge for this black sponge, and provide a vastly increased surface area for biological filtration. The sponge is never discarded or replaced. It is simply cleaned under a jet of water, then rinsed in dechlorinated water, and returned to service in the filter. The motor on a Whisper filter is replaceable, an advantage in the unlikely event that your filter suffers motor failure. These filters may be considered middle-class power filters, and are adequate for most applications.

  Other special purpose filters are useful for special occasions, but do not necessarily constitute the "best" filter for every day use. Among these filters would be Diatom filters such as the System 1, the Vortex, or the Whisper Diatomagic filter. These filters are unsurpassed at removing very fine debris from water, and "polishing" water to a crystal clear consistency. However, the filter media clogs quickly and must be replaced frequently, often as much as every 24 hours. This is not practical for regular, every day filtration. Still, it's handy to keep a Vortex filter on the shelf for special occasions when the tank is full of debris which must be cleared out quickly.

  Small internal filters such as the Duetto or the Fluval internal filter are useful for tanks with absolutely no room for an outside power filter. Unfortunately, their capacity is limited, and they require frequent cleaning.

  Modern corner filters, such as the MicroClean, the Small World, and the Clear-Free appear to be attractive for beginner aquariums. Unfortunately, their cleaning ability is quite limited and the replacement filter media can be quite expensive to replace. I do not recommend these filters.

  Sponge filters are frequently recommended for fry tanks. They are good for this use, since waste materials put out by fry are likely to be in extremely small quantities. The sponge is adequate for this lightweight duty. Fry are well protected by sponge filters. I'm not sure I can see any advantage to a sponge filter over a corner filter, but perhaps I'm missing something. Sponge filters also can be used by fitting them over the intake of power filters, and thus protecting fry from being sucked in. Unfortunately, the sponge filters will eliminate the power filter's great advantage of being able to process large amounts of mechanical filtration. In other words, first we choose a filter for its large mechanical filtration capabilities, and then we restrict this capability. When you look at it this way, the corner filter still makes more sense when used in a fry tank.

UNDERGRAVEL FILTERS:

  This is a very large subject, and I will not go into great detail here. I do intend to discuss undergravel filters in more detail in a separate article. However, a few words are appropriate about the UGF. When first "invented," the UGF was touted as the miracle every aquarist had been searching for. It was supposedly the perfect filter, eliminating all need for other filters. Unfortunately, nothing is ever that simple. UGF filters consist of slotted plastic plates that fit in the bottom of the aquarium. Coarse gravel is poured over the plates, and water is sucked up through riser tubes. These UGF filters can be powered with airstones, or with power filter heads. Water is thus pulled through the gravel, down under the UGF filter plate, and back up into the aquarium, where it exits back into the aquarium. After about 30 days, the gravel becomes "cultured" with beneficial bacteria, and the gravel becomes a giant biological filter. And it does. It really does a great job of biological filtration when set up and operated in this manner.

  Unfortunately, theory and practice often diverge. In the case of the UGF, the plates were designed to operate with a shallow layer of relatively coarse gravel. The UGF works best with about a 1" or 2" layer of pea-sized gravel, about ¼" in diameter. Unfortunately, users often pile up 3" or 4" of very fine gravel, which effectively restricts water flow to a minimum. Unless operated with pea-sized gravel (or any gravel up to "road gravel" size), the UGF will underperform as a biological filter.

  Contrary to popular opinion, UGF filters are NOT maintenance free. Debris from the water pulled through the gravel becomes entrapped in the gravel, where it can decay and pollute the water. The solution is regular maintenance, where gravel over the UGF is regularly "vacuumed" with a water vacuum designed for the purpose, such as manufactured by Python. Additionally, debris and mulm (miscellaneous decaying plant detritis and fish poo) builds up under the filter plate, where it accumulates and eventually forms a layer of sludge under the filter plate. This mulm must be removed on a regular basis, preferably with every weekly cleaning. UGF plates used to come with this information included with the filter plates, but it seems to have been lost over the years. To clean under a filter plate, one must run a length of airline tubing down the riser tubes, start a siphon of water flowing out the airline tubing, and the tubing is twirled and twisted under the filter plates to dislodge the mulm and debris, sucking it out with the siphon action. This must be done at every routine cleaning. It is also possible to remove this mulm to a certain degree by brushing back the gravel and pressing the Python (or similar) siphon tube down against the filter plate. Mulm will be sucked up through the filter plates, and discarded with the waste water.

  UGF plates should be operated in conjunction with a power or other filter to remove mechanical debris. Used in this way, water in your aquarium will remain quite clean and free of toxic waste buildup - but ONLY if you are willing to perform routine maintenance! If you are NOT willing to clean and maintain your UGF, then please choose a different filter method.

  Other filters to be considered are Fluidized Bed filters, often called "Sand filters." Again, advertising hype rears its ugly little head. These filters are touted as being superb filters, providing a "virtually infinite" surface area for bacteria to grow on. Of course, this is nonsense. The surface area of sand can easily be calculated. It's not that much, and certainly not as much as sintered glass materials. FBF filters can be very touch to operate. Too much water flow, and the sand blows out into the aquarium, where it is lost. In the event of a power failure, FBF filters are highly vulnerable to extermination of the desired bacterial colonies. Suffice it to say that if the power failure lasts much more than 12-14 hours, the bacterial colony can be considered as terminated. In its place will grow anaerobic bacteria, to possibly include Botulism. When the filter is restarted (as, for example, when the power comes back on), the sand will probably be blasted out of the filter and into the aquarium. Of more importance, so will the toxic waste byproducts from anaerobic growth. This means if you leave on vacation and there's a 24 hour power failure in your absence, you might come back to a tank with a filter empty of sand and a tank full of very dead fish. Another disadvantage of FBF filters is that they provide no mechanical filtration. Thus, they must be used in conjunction with some sort of mechanical filtration. Since biological filtration is easily achieved by other filter methods, or even by no filter at all, I can't see the advantage of a FBF filter. They are fraught with potential dangers, and are tricky to operate. I'd recommend using a different - and safer - method of filtration.

(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)