CANISTER FILTERS:

  Now we come to the "big guns" of aquarium filtration. These are the filters to choose when you get serious about aquarium filtration. There are some flimsy little filters on the market that represent themselves to be "canister filters," but their extremely limited media capacity (often consisting of nothing more than a little paper cartridge) and flimsy construction make them a joke. When choosing a canister filter, one should look only at heavy-duty filters. This would include the Eheim, the Fluval, and the Ocean Clear line of filters. (Proquatics has just introduced a new line of canister filters that I have not used, but which appear to be very well made. I have no experience with them yet, so I'll ignore them for now.)

  Eheim: the Rolls Royce of canister filters. These over-engineered filters have a history of years of extremely reliable operation. Failures in these filters are so rare as to be statistical anomalies. The Eheim lineup of filter media is simply superlative. Water filtered "The Eheim Way" is polished to a high degree of clarity and freedom from waste byproducts. The media included with the "37-Plus" line of Eheim filters simply cannot be improved upon, and should be installed as per Eheim's instructions. Eheim filters are very efficient, and can perform almost perfect mechanical filtration, vastly superior biological filtration, and (if you choose to run carbon in the filter - I don't) can perform chemical filtration as well as any other filter running carbon. Servicing these big filters is relatively easy, and (thanks to the enormous over-capacity of its filter media) not something you will have to do very frequently with a tank stocked with "normal" volumes of fish. Eheim filters were previously very pricey, but in recent years the price has dropped to very competitive levels.

  As with any other filter, the Eheim (or any canister) filter will run best when it is chosen to be oversized for the tank. I prefer to de-rate my canister filters by as much as ˝ or 2/3rds. In other words, I choose canister filters rated for 60 gallon tanks for my 20 gallon aquariums, or canister filters rated for 150 gallon tanks to use on my 55 gallon tanks, etc. Operated in this manner, canister filters loaf along as they process the water from any tanks.

  Mention should be made here about rated water flow. Unfortunately, all manufacturers rate their filters for "optimum" conditions. That would include operating the filters with no filter media installed (i.e., an empty filter), and with no water rise (the filter doesn't have to life water from below the level of the waterline). This is a fantasy world rating. A filter may, for example be "certified" to provide, say, 400 gallons of water flow per hour. In the real world, after being filled with filter media, the filter will actually process much less water than rated. Thus, the "400 gallon per hour" filter may actually be moving only, say, 125 gallons per hour. This makes comparing filters by rate of water flow a ridiculous deception. Rules of thumb abound for recommended rates of water flow, anywhere from 1 water change per hour, up to 10 times water change per hour, or anything in between. If you have a 55 gallon tank, you might select a filter rated for, say, 300 gallons per hour. This would mislead you into thinking that you are going to get 5 or 6 water changes per hour. You won't. In fact, your filter may actually only provide 2 water changes per hour. This is because rates of water flow are always greatly exaggerated.

  Fortunately, "adequate" water exchange rates are much lower than you have been misled to believe. If you think you're getting, say, 10 water changes per hour, but are only getting, say, 3 or 4 changes per hour, don't worry. That's still perfectly adequate for processing out debris and biological wastes. You don't need more.

  Eheim is the ONLY manufacturer that provides realistic rates of water flow. Unfortunately, they don't do that in their advertising, but instead list it on the actual box that holds the filter. Thus, say, and Eheim 2217 is rated in advertising for, say, 260 gallons of water flow per hour. On the box, you will quickly discover that the actual flow is about 112 gallons per hour. Is this adequate? Absolutely. However, it's why I deliberately de-rate the Eheim 2217 as being perfect for a 55 or 60 gallon aquarium. It certainly can handle a much larger tank. Experience has shown that the Eheim 2217 is perfectly capable of handling the filtration of a 200 or 300 gallon tank. Why is that? Because those "rules of thumb" you have been told about are misleading. In actual practice, a water change of once per hour, or even a little less, is perfectly adequate for an aquarium with a "normal" fish load.

  Fluval filters have come a long way in recent years. Originally, these filters had a design that, although of high quality, had some built in problems. Notably, Fluval filters could sometimes be difficult in priming them (getting air out of the system). Fluval owners quickly discovered they had to learn how to rock the filter back and forth to free trapped air. Sometimes this went well, and sometimes not. Still, the filters were considerably cheaper than Eheim, and they tended to be very reliable, giving excellent service for many years. If I had to name one fault of the Fluval filters, I would have to point to the filter media provided. The order of media changed occasionally, indicating Fluval wasn't too sure about which was the best order to fill the baskets. Eventually they settled on running ceramic rings in the bottom, to break up and trap large debris. The middle basket held GAC. This carbon could be run as a chemical filter, or it could be allowed to run indefinitely. After about 30 days, the carbon ceased to function as a chemical filter, but it became a very excellent biological media. The top layer was two sponges of open pore construction, to provide some additional mechanical and biological filtration. This arrangement worked very well, but could not rival Eheim's media. Indeed, two tanks of the same size, set up side by side, one filtered by Eheim and one filtered by Fluval, would immediately demonstrate that the Eheim filtered water to a much higher level of clarity. Fluval water appeared adequate and clear… until it was placed beside Eheim filtered water. At that point, the difference in filters was quite noticeable. Nevertheless, the Fluval was quite adequate, and considerably cheaper to purchase than the Eheim. For a given size, the Fluval often cost less than half the Eheim. Arguments were also made that the Eheim filter design made water bypass impossible (which was true), while the Fluval allowed water bypass (which was also true, but not to a significant degree).

  In recent years, Fluval has pretty well closed the gap. With the introduction of the x04 series of Fluval filters, combined with the development of BioMax, Fluval can now hold its own against Eheim in almost every department. As usual, many possibilities exist as to how to run Fluval media. With the x04 series of filters, you really have no choice about your first stage: it's going to be sponges. This isn't really as big a problem as some would have you believe. Open pore sponges serve as very good mechanical filters, and also perform a lot of biological filtration (after they have been in use for about 30 days). The media baskets allow complete personalization of media. Many arguments exist for doing it this way or that. If you like to use carbon in your filter, the bottom basket would be a good place to run that. BioMax provides a tremendous surface area for bacteria, and one could not be faulted for filling all the baskets with nothing but BioMax. Water filtered in this way would be exceptionally clean and clear.

  Personally, I like the Eheim method of filtering water. Therefore, I have filled my Fluval filters with Eheim media, in the order they recommend. I put Ehfimech in the bottom basket, and fill the middle baskets with Ehfisubstrat. The top basket is run with ˝ Ehfisubstrat, and ˝ polyester filter floss. Water filtered through Fluval filters arranged in this manner cannot be differentiated from Eheim water. Clarity and purity are excellent.

  Which canister filter to buy is pretty much a personal choice. I own both Fluval and Eheim filters, and I'm delighted with both. If I were to purchase another canister filter today, I'd have to give some serious thought about which to buy. However, I believe I would probably purchase an Eheim filter, if only for its long reputation of reliability, and its "over-engineered" construction. I don't believe the Eheim "Classic" series of filters can be improved upon. Their performance is superb, and no customization of media is necessary.

HOMEMADE FILTERS:

  Another option open to the aquarist who is handy with simple construction projects is the homemade filter. Indeed for very large tanks, or small ponds, homemade filters are much more cost effective than commercial filters. Beyond a certain size (probably 300 gallons or so), commercial filters become prohibitively expensive, while homemade filters are quite affordable.

  The problems confronted in home filter construction is to provide a large quantity of filter material, to move water from the tank to the filter, and then return that water to the tank. Of course, the entire assembly should be waterproof and durable.

  Many solutions are possible. When designing your homemade filter, you'll want to choose a waterproof water pump that can pull water from the tank and feed it up a length of plastic hose to the filter. The water should enter the filter at the bottom of the container (garbage can?). There should be a raised area inside the container, one that leaves the bottom 6 inches or so of the can raised and free of filter media. Waterproof plumbing fixtures with threaded ends allows the intake hose to be safely attached to the container. The media can be raised off the floor of the tank by way of plastic (waterproof) blocks of some sort. Over these blocks, place 2 layers of plastic "eggcrate" material (as sold in electrical departments of hardware stores and intended as fluorescent light diffusers. Next fill the filter container with any media you desire. Commercial plastic filter media , the kind sold in little spiked balls, can be used. It is lightweight and readily available. However, if you find you need 25 gallons or so of these plastic balls, you may quickly discover your budget can't afford them. No matter: any plastic media that provides a large surface area (to support biological growth) is sufficient. Provided on your sources, and how much (or little) they cost in quantity, you can run plastic hair curlers, or plastic shotgun wads (the kind with the little spoked base), or cut-up soda straws, or shredded plastic milk jugs, or shredded juice containers… just about anything that's waterproof, non-toxic and available to you cheaply in large quantities will serve as a great biological media. Another possible filter media is decorative Lava Rock. Sold in 100 pound bags at Walmart, Lava Rock is somewhat porous and presents a huge surface area for colonization of bacteria. Run a layer at least 12" or 15" deep. Water will be force up through all this media you have provided, and out another opening you've cut in the side of the container, a few inches below the top of the container. Another hose fitting, and you're ready to allow the water to flow by gravity back into the tank. This assembly may not be aesthetically attractive, but it will be functional. If appearance is important, you can always build a simple enclosure to hold the filter above the back or side of the tank. Whatever you choose, be sure to keep the filter above the tank, not below, so that gravity will work for you and prevent the container from overflowing by providing an outlet near the top of the container to return filtered water to the tank.

  Of course, other possibilities exist. A search of the web for "diy filters" will turn up many sites where the author has built his own homemade filter.

  Which of these filters is for you? Well, that's your decision to make. Each filter has its fans, but many people have chosen filters because of attractive claims made by advertising agencies, and not because they fully understood what their filter was capable of doing. However, this discussion will help you to make a more informed decision so that you choose a filter you can be happy with for years to come. Just remember not to buy too small, and don't buy too cheaply. A quality filter will serve you well for years; a poorly designed filter will remind you of your poor choice every day for years to come.

  NITRATES: We mentioned that all fish waste (ammonia) eventually are converted to nitrites, and then to nitrates. Nitrates cannot be filtered out of the tank with any of the usual filters. To remove nitrates, you have several choices such as specially constructed anaerobic filters, denitrification by electrolysis, algae filters, or denitrator filter pads that have a finite ability to hold nitrates and must be cleaned or replaced regularly.

  Fortunately, there is a simpler method: water changes. Nitrates should not normally exist in tapwater, although they may if you live in a farming community and derive your aquarium water from shallow wells. Water changes will remove all waste byproducts by the process of dilution. The maximum desirable nitrate level for most freshwater fish is 20 ppm (Parts Per Million). If your nitrate levels are, say, 40 ppm, then a 50% water change will drop the tank nitrate levels to 20 ppm. If your nitrates were at 80 ppm, then you would need to remove 75% of the tank's water, and replace with fresh water. The resulting mixture would have a nitrate level of 20 ppm. After recalculating your nitrate levels every few weeks, you'll soon be able to figure how much water you must replace on a weekly basis to maintain a nitrate level of 20 ppm (or less).

  An aquarium that is filtered with a quality mechanical filter is most of the battle. The biological filter capabilities of filters are of much lesser concern, since biological filtration can be taken care of in the tank with no filter at all. Sintered glass materials do improve the biological filtration capabilities of any filter. Chemical filtration is probably not something that you will always want or need in most tanks, and regular water changes all but eliminate this as a criteria for choosing a filter. Therefore, when choosing which filter is right for you, evaluate it on the basis of how good a job it can do as a mechanical filter. All the other requirements will then fall into place.

(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)