An aquarium filter should
- be quiet
- keep the water surface in motion for oxygen exchange
- remove floating crud from the water (mechanical filtration)
- turn ammonia from fish waste and leftover food into nitrate
- remove strange odors and chemicals (chemical filtration)
- kill free-floating algae and parasites (sterilization)
- heat the water in a tropical tank -- this is not necessary for
Goldfish and other coldwater animals
Noise in an aquarium filter comes from several sources. First is the
flow of water back into the tank. Generally you want the filter output
to be at the surface of the water so that it breaks up surface tension
and keeps the surface moving fast enough to facilitate oxygen exchange.
Fish consume oxygen and the aquarium water needs to be able to pick up
additional oxygen from the air on top of the tank. A high-speed
waterfall into the tank isn't going to be especially quiet, however, so
you want to make sure that either the tank level won't fall due to
evaporation or that the filter return can be easily pushed down a bit as
the water level falls.
Another way to reduce the noise of water flow is to reduce the volume of
water flow. This becomes possible when you have a filter that is able
to do a fairly complete job on water in one pass. With such a filter
you might only need enough flow to change the tank water twice per hour
rather than four or five times per hour.
A final element of noise control comes from the filter design itself.
Where is the pump? How high quality is the pump? Is the pump submersed
in water or out in the open?
The standard method of achieving surface agitation in a fish tank is via
air stones and an air pump. These put air bubbles in the water that do
not facilitate oxygen exchange as they bubble up but that do a superb
job of breaking up the surface as they exit the tank. Unfortunately
even the fanciest air pumps for sale in the US are extremely noisy,
perhaps 10 times louder than a high-quality filter. Thus, if you can
achieve adequate surface agitation with your filter output, that is a
much better solution than adding an air pump.
My personal favorite technique relies on positioning a spray bar along
one horizontal edge of the tank, opposite the filter intake. This
results in a surface current running the entire length of the tank. (A
spray bar is merely a tube with a bunch of holes in it, all pointing in
the same direction, like a flute.)
Note that in a planted aquarium you don't need or want as much
agitation. The plants generate some oxygen for the fish. The plants
need carbon dioxide (CO2) gas to survive. Heavy agitation tends to let
the CO2 escape.
Mechanical filtration involves pushing the tank water through a strainer
of some sort, either a Mr. Coffee-style paper filter or a sponge or
"filter floss". Anything that had been floating around clouding the
tank will now be trapped on the filtration medium. Keep in mind that
anything trapped in the medium is still part of the ecosystem. It is
decomposing and putting organic waste into the tank; you just can't see
it anymore (this is why the saltwater fanatics use protein skimmers,
which pull crud off the surface of the water and get it out of the tank
More or less any waste in the tank manifests itself as ammonia. In a
heavily planted tank, this may be consumed by the plants. Otherwise,
nitrifying bacteria go to work to turn the ammonia (toxic) into nitrite
(toxic) and then into nitrate (not so toxic). This sounds like the most
complex element of aquarium filtration and indeed it can be problematic
during the first month or two when the tank is "cycling". However, it
turns out that biological filtration is the least critical kind in an
established tank. The bacteria are happy to live in almost any medium
as long as they are supplied with flowing water.
If you change your water frequently, it is unclear why you'd ever need
chemical filtration. The general idea is to put carbon into the tank
temporarily to absorb various chemicals. But carbon also removes
minerals, some of which may be necessary for your fishes' health and
many of which, e.g., iron, are definitely required by plants. Serious
aquarists tend to use chemical filtration only when they have some idea
of what they are trying to achieve, e.g., when they want to clean a
funny smell out of the water.
In an ideal world, anything that is alive when it goes into the aquarium
filter will be dead when it comes out. There are a fair number of
parasites that must float free in the water to be transmitted from fish
to fish. You want them dead. Algae grows to some extent on rocks and
tank walls but it takes much longer to overwhelm a tank if it cannot
live in a free-floating form. Aside from cost ($100-200), there are no
drawbacks to water sterilization and yet only one commercial filtration
system (see below) incorporates it as a matter of design. This is odd
because it is much harder to maintain an unsterilized tank--you're
constantly scraping algae. The more light that the tanks gets, e.g.,
from a nearby window, the more you need sterilization.
There is only one sterilization technology available today: ultraviolet
light. Water is passed in close proximity to a very bright UV bulb and,
if the flow is sufficiently slow for the bulb power, this kills most
parasites and algae.
Most tropical fish like to live in water between 75 and 85 degrees
Fahrenheit, depending on the species. Room temperature in your house is
probably closer to 72 degrees. Pumps and lights will heat the water to
some extent but unless you're keeping coldwater fish such as Koi or
goldfish, you'll want a heater for precision control of tank
temperature. You can shove a heater into the tank but it will be (a)
ugly, (b) vulnerable to breakage, and (c) likely to heat its corner of
the tank more than the rest of the aquarium. It makes a lot more sense
to heat the water as it flows through the filter.
Now that we've covered the fundamentals, let's review some specific
Eheim Canister Filters
An Eheim canister filter sits behind or underneath the aquarium and
connects via hoses. These are by far the world's highest quality
canister filters and the motors are extremely quiet when new, almost
always quieter than the flow of water into the tank. It is tough for
water to bypass the sponges and other mechanical barriers inside the
canister and therefore the filtration per pass is thorough. This means
that the water flow need not be brisk for effective filtration.
Eheim is the only company making canister filters with integrated
heaters. Only a handful of Eheim's models provide this feature but
those units are adequate for tanks up to 150 gallons or so (and you can
always use two on a larger tank). If you decide to get an Eheim,
definitely choose the latest "Profi II" models, which include a priming
pump on the unit and some other nice advances. For most aquaria, you
can safely ignore the Eheim Wet/Dry units. A standard Eheim provides
more than ample biological filtration--a test kit will register 0 ppm of
ammonia--along with the mechanical filtration that you need and chemical
filtration if you stuff in some carbon. The Wet/Dry units provide
massive biological filtration capacity but not the critical mechanical
filtration that your tank needs.
Servicing an Eheim is very easy and clean. There is a
disconnect/shutoff level where the tubes meet the filter so that you can
carry the canister into a bathtub, kitchen sink, or utility sink and
handle the wet job of changing filter pads, cleaning out debris, etc.
Sadly Eheim seems to ignore the whole issue of UV sterilization. You
can pipe the output of an Eheim canister into a UV sterilizer but the
resulting setup will involve custom plumbing pieces and won't look very
Smaller Warts? My personal experience with Eheim has been that the
motors begin to buzz a bit after a few months of operation. The buzzing
is audible in my bedroom tank though still quieter than the water
outflow. Eheims are made in Germany and, by the time they are imported
to the US, are much more expensive than other brands of canister
filters. Consequently it is difficult to find a shop to sell or support
the product. The www.eheim.com Web
site is invariably out of date and they don't bother to answer questions
submitted via their contact form. Nor do they list their phone number!
If you want accurate product information, the German site is a bit
better: www.eheim.de. Given the many
choices of media for an Eheim canister and the lack of manufacturer
support, it is a good thing that the US retailers who stock Eheim tend
to be among the higher quality shops.
Marineland Eclipse Bio-Wheel Hood
Marineland makes a variety of hoods in standard sizes that combine
lighting and filtration. These are variously named "Eclipse" and
"Bio-Wheel" depending on size. The function is very similar to a
hang-off-the-back-of-the-tank power filter, but everything is
contained on top of the tank within a relatively inexpensive plastic
hood. This should be perfect for a tank intended to be viewed from
Here are the problems with the Eclipse/Bio-Wheel hoods:
More: a design for a better aquarium hood.
- mediocre mechanical filtration, laughably poor compared to a
canister filter, which leads to annoying small particles floating
around the tank
- no heater, despite the fact that nearly every fish tank needs a
heater, so you'll have at least one ugly piece of eqiupment in the
- no UV sterilizer; there are submersible UV sterilizers with
built-in pumps, but again you'd have another ugly piece of equipment
in the tank
- no way to add an automatic fish feeder
- cheap construction and difficult-to-obtain spare parts
- many users have complained of condensing water flowing down the
outside of their tanks (possibly a problem with fit or water level?)
- somewhat generic lights; not bright enough for a reef or planted aquarium
If Eheim is the apex of prissy European engineering, designed to look
good in your living room, Rainbow Lifegard (www.rainbow-lifegard.com)
is the American sledgehammer
of filtration systems, capable of filtering aquaculture ponds and public
aquariums. When you get a Rainbow Lifegard system for a home aquarium
you're buying the very smallest products in the company's line.
The Lifegard system is modular and provides the only complete filtration
solution by the standards listed at the top: mechanical, biological,
chemical, heating, and sterilization. The Lifegard Quiet One pump is
extremely quiet, on a par with the Eheim canisters. If its flow rate
does not meet your needs, however, you can use just about any other
aquarium pump with the Lifegard modules.
Filtration in a Lifegard system usually starts with mechanical. Water
has to make it through a Mr. Coffee-style heavy paper filter,
cylindrical in shape with pleats. Unlike some competitive designs, each
pleat in a Lifegard filter is supposed by a plastic subframe. This
keeps the pleats from collapsing as the filter ages. Consequently a
Lifegard mechanical filter can go for several months without service
where a Marineland pleated filter might need replacement after two
weeks. The downside to this subframe is that it makes filter
replacement rather more complex. You can do it in one minute but each
pleat must be seated over the subframe. The whole process is much
easier if you are working with completely dry materials, so budget to
keep a spare filter carrier in a drawer. If you have enough space, I
recommend getting a double or triple-length Lifegard mechanical filter
module. You won't have to service it as frequently as the standard
The Lifegard chemical filter is essentially a big open chamber. You can
fill it with carbon, peat (to soften water for Discus), or some sort of
substrate for nitrifying bacteria.
For heating, Lifegard makes an empty plastic module into which you slip
the heater of your choice. If the heater breaks or is corroded by
saltwater, you toss out the $30 heater not the $500 filtration system.
Lifegard makes its own line of UV sterilizers in a variety of sizes and
wattages, from 8 watts to 240. For an aquarium up to 250 gallons you
probably want at most the 25-watt model.
The Rainbow Lifegard system has been around for many years and I've
never heard about an unhappy customer.
The worst thing about the Rainbow Lifegard system is that it is so
flexible and comes in so many pieces. The average pet store won't stock
it at all or won't have all the pieces that you need for a complete
system. Until Rainbow Lifegard comes out with pre-packaged systems, it
may be best to buy from a shop that will put together and install your
Lifegard system. On the plus side, the
contains comprehensive information and the California-based company
provides excellent support to consumers.
My personal experience with Rainbow Lifegard has been on a 90-gallon
planted aquarium in an office building. Here's what I found:
If you decide to take the Rainbow-Lifegard plunge, I recommend getting
an Eheim spray bar or fabricating something on your own. If the pump
noise/output is too much for your tank, it may also be worth looking at
wimpier pumps--any pump with a standard 3/4" thread will fit the system.
- assembly and installation required three hours, one of which was
spent fighting leaks in the Teflon tape-wrapped threaded plumbing
connections that I'd made (Rainbow Lifeguard offers a system based on
PVC glue connections as an alternative and this is preferred by many
- the instructions that came with each component were pretty good but
if you don't have an overall understanding of how the system works,
you'll need some luck, some thinking, and the Web site to get everything
in the right order
- the Quiet One pump, marked "Silent Aquarium Pump" on the housing, is
not silent. I couldn't hear any mechanical noise from the pump but, for
the first hour or so the sound of water rushing through the pump was
easily audible from 8 feet away in a normal office environment
(computers and HVAC system operating nearby). Curiously this rushing
noise various to some extent with time, perhaps because of trapped air?
[The pump is much quieter than the TetraTec filters described above but
definitely noisier than the small Eheim canisters, which pump only about
one fifth as much water.]
- the Quiet One pump, rated at more than 1000 gallons per hour with
zero head, is overkill for a 90-gallon tank. With the system hooked to
the over-the-side plumbing kit supplied by Rainbow-Lifegard, the result
was rather like putting a firehose into the fish tank.
- the ballast for the UV sterilizer makes a very slight 60 Hz. hum,
much much quieter than the rushing water noise through the Quiet One
pump but audible
In 2002 Rainbow-Lifegard has plans to offer an improved over-the-side
plumbing kit, substantially better instructions, some pre-assembled
systems, and a better Web site.
My personal bottom line on the Rainbow Lifegard system is that it works
great but is noisy enough that I would want to make sure that the pump
and UV sterilizer ballast were in an enclosed cabinet or closet.
Another canister filter worth considering is the Rena Filstar Series. These filters run quietly, work well, and are easy to maintain. They probably are not as good as the Eheims...but they are less expensive and many Fish Store carry them.
-- Will Hoerl, March 13, 2003
I've been keeping fishes for 20+ years, including breeding pedigreed goldfishes, bettas, cichlids etc. The easiest and least maintenance filter I have is my present setup: none. ... actually it's java moss (tons of them) in a 100 gallon tank. I change the water once a quarter, and the only maintenance I do is to refill water lost to evaporation and to remove excess java moss. I know the latter is excessive when the fishes can't swim around but are trapped by the moss. The fishes are low maintenance fishes like comets, shubunkins caught from my pond with plecos and some SAEs.
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