From: tli@caldera.usc.edu (Tony Li)
Newsgroups: alt.aquaria,rec.aquaria,sci.aquaria
Subject: FAQ: Filters
Date: 16 Apr 1992 01:05:04 -0700
Organization: University of Southern California, Los Angeles, CA
Reply-To: tli@cisco.com,patti@hosehead.hf.intel.com
NNTP-Posting-Host: caldera.usc.edu


				  Filters

Rev 1.2  10/4/91

Prologue:
---------
This monthly series is intended to address some of the frequently
asked questions (FAQ) on the rec. and alt.aquaria newsgroups.  Because
the answers may not be complete, please feel free to ask questions. 
This is only intended to address first level concerns, and not to
dampen discussions.

Currently, the series contain the following messages:

     > Beginner topics - Glossary of terms (used on the net)
                       - Setting up an aquarium
                       - Moving an aquarium
                       - Good beginner books

     > Equipment       - Filters and related issues
                       - Air pumps

     > Water Quality   - Nitrogen Cycle
                       - Plants
                       - When your fish are sick

     > Mags and MO     - Magazines, subscription rates and
                         addresses
                       - Mail order outfits.

Please review and send any corrections or inputs to the FAQ maintainers
with "(FAQ)" in the subject line.  You are absolutely welcomed to tackle
(i.e. WRITE) sections that have not been written yet.

I've received recommendations to put email address "pointers" in
the FAQ to vector questions to specific experts on particular
subjects.  If you would like to offer yourself as such an expert,
please send me your email address and the specific topics you want
to host.  Please include an email path that is generally accessible
to the greatest number of people.

FILTERS AND RELATED QUESTIONS:
------------------------------
     Filtration is very important to the welfare of your guests,
and as such there are many different kinds of filters.  Since there
are many brands and opinions, one should post requests for
recommendations.  Equipment that is typically found on advanced
aquarists' systems are also noted.  These are typically more
expensive, and are generally not needed by, nor recommended for
beginners.
     In general, if one needs to rinse/wash filter media, one
should never use soap or hot water (or for that matter, very cold
water).  This would serve to kill the beneficial bacterial colonies
in the filter media.  (See nitrogen cycle).  Use the reject water
siphoned out your aquarium to wash/rinse filter media.
     The following filter discussions are arranged alphabetically,
with related topics grouped arranged separately at the end.

BUBBLE UP FILTERS
     These are specific examples of internal filters.  These use
streams of air bubbles to push water up and out of a tube, thereby
creating a pull of water into the filter through the filter media. 
(See INTERNAL FILTERS).

CANISTER FILTERS
     These are large plastic "canisters" typically located outside
of and under the aquarium in the cabinet. They are designed with a
powerful pump which draws water through an in-take hose located in
the aquarium, pushes it at a relatively high pressure through the
filter medium, and forces it back to the aquarium through the
return hose.  (Many times, this water is sprayed across the surface
of the water to create aeration).

CHEMICAL FILTERS  (advanced)
     Ion exchange resins are used to deionize new water.  Also,
synthetic resins designed to adsorb specific ions (like phosphates,
or nitrates, or sulphates) are now available.  See ads in FAMA and
other such magazines for new items.  Thiel has chapters on chemical
filtration in his books, so does Moe (see Books).  Carbon is also a
form of chemical filtration.

DIATOM FILTERS  (advanced)
     These can be described as purely mechanical filters.  It
relies on the diatomaceous earth (skeletons of tiny animals called
diatoms [di-atom = two atoms/parts]) which "cling" onto dirt and a
fine mesh screen to capture the "dirty" diatoms.  Because of the
efficiency, diatom filters are also called water polishers.  These
are not used over long periods (they clog up very quickly), and
hence cannot be considered good biological filters.

EXTERNAL FILTERS
     Oftentimes, this is used to denote power filters.  But this
not always the case.  (See POWER FILTERS)

FOAM FRACTIONATION
     See PROTEIN SKIMMERS.

INTERNAL FILTERS
     These filters are plastic cartridges that fit inside the
aquarium.  Dirty water is drawn into the filter through slits
located on either the top or sides of the body.  The method of
water propulsion can be motorized, or bubble driven.  Maintenance
of these filters can be difficult.  Many times, as one lifts the
filter out of the aquarium, dirty water backwashes out into the
tank.
     Some designs, like Lee's Triple Flow and similar models by
Penn Plax and Marineland do not have this problem.  They also cost
more, of course :-)  Also, one has to immerse entire appendages
into the tank to access the filter.  This type of filter is only
recommended for up to 20 gallons.  You may be surprised how
inexpensive external power filters (EPF) can be and how quiet they
are.  Always consider power filters unless you are raising fry,
spawning live-bearers or killies in a "natural" setup, or need
minimal flow (for spawning bubble-nest builders).

MECHANICAL vs. BIOLOGICAL
     Almost all filters perform mechanical filtration, and most
perform biological filtration.  The difference between these is
that mechanical filters will capture and remove suspended particles
from the water, clearing the water in the process. (The filter
media obviously becomes dirty, and must be cleaned every once in a
while).  Biological filters provide habitats for beneficial
bacteria that breakdown nitrogen compounds from biological waste
into progressively less toxic forms (ammonia -> ammonium ->
nitrites -> nitrates - > nitrogen).  (This is a gross over
simplification.  See nitrogen cycle in H20 quality).

POWER FILTERS
     This is the common name for filters that hang on the back of
the aquarium.  Two basic types exist.  In one case, water is drawn
through siphon action into the filter media, and expelled by a
pump.  In the second case, water is drawn by a pump into the filter
media and the allowed to trickle back into the tank.  A major
benefit of such a filter is the ease of maintenance.  The location
and design of the filter allows for quick and non-messy removal of
dirty filter media.

PRE-FILTERS  (advanced)
     This are filters used primarily to remove most of the
particles from the water before it arrives at a primary filter,
which may be located in a difficult to clean area.  The filter
media on pre-filters are removed and replaced easily, thus reducing
the number of times one has to change/maintain the media in the
primary filter.

PROTEIN SKIMMERS  (advanced)
     Protein skimmers, also known as foam fractioners, are an
unusual type of chemical filter.  They are primarily used in
marine aquaria, because they require the formation of foam which
form more readily in salt water.  Protein skimmers can be used in
freshwater, but will be less efficient, and may require greater
flows of air to produce sufficient foam.  They remove from the
water a wide variety of organic compounds (e.g.. proteins) that
normally collect on the surface of the tank water.
     These compounds, surface active molecules, are attracted to
the air-water boundary by their molecular structure.  Large amounts
of these compounds are often visible to the aquarist as slicks,
sheens, or thin scum on the tank surface.  In addition to the
presence of films on the surface of the water, an abundance of
these compounds is signalled by increased stability of bubbles
floating on the water.  This stability can result in large rafts of
bubbles spanning the surface of the tank, and very large bubbles
grown from many successive merges of smaller bubbles.
     A protein skimmer consists of a space where fine air bubbles
are encouraged to mix with circulating tank water, and a means for
collecting the resulting foam and removing this foam from the tank. 
Typically, a mist of fine bubbles is allowed to rise in a column of
circulating water, forming foam in a small chamber at the top of
the column.  This foam rises upwards through a narrow opening, and
flows into a collection cup which must be periodically emptied.  In
a properly adjusted protein skimmer, some amount of foam is present
all the time in the chamber, but will only rise high enough to
reach the cup and be collected when surface-active compounds are
present in sufficient quantity to stabilize the foam.

REEF FILTERS  (advanced)
     See WET/DRY FILTERS.

REVERSE UGF  (advanced)
     This uses the same gravel plate as a regular UGF except that
water is pumped down an uplift tube (in this case a misnomer),
under the plate, and then *UP* through the gravel.  The water
traveling through the uplift tube must be clean, since it would be
very difficult to clean under the gravel plate.  The water can come
from the output of a filter (canister filter for example), or can
come from a new generation of powerheads (submersible centrifugal
water pumps) has a "reverse flow" feature which makes it easier to
use them for reverse flow UGF.  (See POWERHEADS).  The powerhead
should be outfitted with some sort of pre-filter such as a sponge.
     Since the filtration will have been taken care of already, the
reverse UGF is primarily a biological filter.  It has the alleged
benefit of keeping fish filth suspended in the water for the
filters to suck up, and thereby reducing required maintenance on
the gravel itself (i.e. dirt does not accumulate in the gravel).
     Because most aquarium equipment was not designed to work in
this manner, one typically has to rig up one's own hose adaptors to
connect the output hose to the uplift tube.

RO FILTERS  (advanced)
     These purely mechanical filters that are used to purify water
from the tap before introduction into the aquarium.  These devices
use a thin membrane that only allows water molecules (and a few
other smaller dissolved ions) to pass through to the output.  The
unwanted water and materials are redirected to the drain.  This
filtration method wastes water.  RO Filters can also be found at
building supply stores since household drinking water filtration
also uses the same technique.
     There are two common types of RO filters sold.  One uses a
cellulose tri-acetate (CTA) membrane, and the other uses a thin
film composite (TFC) membrane.  The TFC membrane is the best for
aquarium use.

SKIMMER (see Protein Skimmer) (advanced)
     This term can refer to surface skimmers as well as protein
skimmers.  Surface skimmers are essentially boxes set just below
the surface level of the aquarium.  Water "spills" into this box
and is drawn out to a filter (by siphon or mechanical means).  This
oftentimes removes the surface "slick" found on marine aquarium.

SPONGE FILTERS
     These are open cell sponges that are connected to some
mechanical device (bubbler, power head, pump etc.) that will draw
water into the sponge.  Because of the large surface area/water
flow ratio, the suction is not strong enough at any given point on
the sponge to trap fry or other small fish (as opposed to, for
example, the intake hose of a canister filter).  These are often
used for breeding tanks etc.  Fish filth is trapped in the sponge,
which is rinsed every once in a while for maintenance.  Most
sponges are shaped in such a way that, as filth clog up particular
areas, the suction collect waste in other areas.  The sponge also
serves as a biological filter.

TRICKLE FILTERS  (advanced)
     See WET/DRY FILTERS.


TURNOVER RATE
     The number of times the volume of water in the tank should
pass through the filtration system in an hour.  The general rule is
3-5 tanks/hour, unless the fish load is very light, in which case
.5-1 tanks/hour is OK.  Cannister filter instructions suggest 1-2
tanks/hour.  High turnover rates are probably beneficial (more
filtration), as long as the fish are not swimming for their lives
constantly.

UNDERGRAVEL FILTERS (UGF)
     This filter is a plastic plate with holes/slits that is placed
first in the aquarium, after which gravel is poured on top.  Water
is drawn through the gravel, and impelled up and out through uplift
tubes (typically located in the rear corners of the tank).  The
impelling method could be bubblers or power heads.  The gravel
becomes the filter media for both mechanical and biological
filtration.  This means that the gravel should be "vacuumed" every
once in a while.  As the gravel becomes clogged, water bypasses the
clogged areas, and these become sites for unhealthy bacterial
activity.
     There has been much debate over the use of UGFs.

WET/DRY FILTERS (advanced)
     These filters enhance the metabolic activity of the beneficial
bacteria by providing good conditions for their growth.  These are
very much in favor with marine aquarists, especially reef aquarists
whose guests require clean stable water.
     The principle of operation is as follows:  Water is sprayed
(by a revolving spray bar) or trickled/dripped (by a plate with
lots of holes) over a media that is largely exposed to air (i.e.
not immersed in water).  As the relatively random patterns of water
trickle over the media, the large surface of the media is
constantly kept wet with a thin film of water.  The large surface
area can dissolve lots of oxygen and may de-gas (expel) a number of
other things, most notably ammonia (NH3) and CO2.  The media houses
lots of bacteria which takes the oxygen and converts NH3/NH4+ into
NO2- (nitrite), and NO2- into NO3- (nitrate).  This is the "dry"
phase.
     The "wet" section is a submersed media which can be one or
both of the following: a purely biological filter, or a
denitrification filter.  A number of sources have been suggesting
that it contributes more to oxygen depletion than to any meaningful
nitrification.  A denitrification filter is created by placing a
large submerged sponge in the path of the water, allowing some
water to *slowly* flow through the sponge, while most of the water
passes over it.  In the nearly anaerobic cells of the sponge,
nitrites are converted to nitrogen by Pseudomonas and other
bacteria (however, Thiel and others have been very critical of this
method of denitrification); chemical "augmentation" -- a dolomite
or other calciferous material is used to leach calcium carbonate
into the water to replenish  what gets metabolized by plants; and
supplemental filtration, like a bag of activated carbon or some
Chemi-Pure. 

     The water which is relatively depleted of oxygen, is passed
into the wet phase, which supposedly converts the NO3- into
nitrogen and some oxygen.  This water then gets pumped back into
the tank.
     Wet/dry filters are not cheap, and because of this, the net
contributors often come up with suggestions for rolling your own. 
Keep your eyes peeled for these messages.

Filtration Related issues:
--------------------------

AIR FILTERS
     Some aquarists take the output of air pumps and bubble the air
through water in a closed jar.  The air is then taken through the
lid into the aquarium bubbler.  This serves to dissolve air borne
chemicals (such as mineral oils from the pump) in the jar water
before it gets into the aquarium.  Also useful for households that
have smokers.

GRANULATED ACTIVATED CHARCOAL/CARBON
     These are small pellets of carbon manufactured from organic
material (such as bones).  These pellets contain microscopic
caverns that are the right size to trap certain molecules or ions
(called adsorption as opposed to absorption).  After a period of 3-
6 months or so, the carbon becomes ineffective.  It cannot be "re-
activated" by heating in your home oven unless you have a blast
furnace at home.

OZONE
     Ozone is a highly reactive form of oxygen, and it is bubbled
through water in a special reactor to oxidize organic waste
material and some toxins (rendering them less harmful).  Since it
is so reactive, it is invariably bubbled through carbon (so
leftover ozone forms carbon dioxide) before being released into the
atmosphere.

PEAT
     This is an organic material made of composted forest fibers. 
Peat is rich in humic acid and tannin, and is sort of like tea. 
Its effect on water similar to tea.  It softens water and leaves
the water slightly acidic (and yellow).  It is used for lowering
and buffering water for sensitive fish.  Peat also helps chelate
some metals and make them usable by plants.  There are two
varieties of peat available: "normal" peat which consists of small
particles (much like peat used in gardening) and *fibrous* peat
that looks like a bunch of long strands and twigs (this is
sometimes referred to as "German" peat and it is nearly impossible
to buy in this country except in tiny, extremely overpriced
packages of Fluval and Eheim brand in aquarium shops.
     Garden peat can be bought dirt cheap in bulk from garden supply
stores.  MAKE SURE IT HAS NO FERTILIZERS OR FUNGICIDES -- these will kill
your fish.  According to Oleg Kiselev, Canadian peat, especially "Sunshine"
brand, seems to be safe.  Oleg has also used "Black Magic" gardening peat
with equal success.  ALWAYS RINSE PEAT BEFORE USING and many books
recommend you boil it a few times, too.  Oleg usually boils peat 3-4 times
and stores it wet.
     Peat is very important for killifish spawning.

POWER HEADS
     These are miniature pumps that draw water through uplift tubes
(associated with UGFs) and impel it into the aquarium.  They often
come with a feature that allows air to be drawn into the outflow
resulting in a fine mist of bubbles.  (This is due to something
called Venturi action).  The water output can usually be directed
in any direction, and up or down.  Some even have a reverse feature
for Reverse UGF systems.
     Although sometimes used as pumps, these are not really
designed to push water up any distance.  They are designed to draw
water and push it out laterally.

UV STERILIZERS
     Ultraviolet light sterilizers are used in series with  filters
to kill water borne parasites (such as ich) and/or bacteria. 
Although not strictly a filter, it does ultimately remove harmful
organisms.  When used in reef tanks or breeder tanks where the
occupants depend on microscopic organisms in the water for food,
these should not be turned on during feeding time.

ZEOLITE
     Zeolite is a naturally occurring mineral that can exchange
"hard" metallic ions (like magnesium and calcium) for soft metallic
ions (like sodium).  This softens water.  Zeolite also adsorbs
ammonia.  Zeolite will not work in salt water.  It is reactivated
by immersing it in a strong salt solution for 24 hours.

AIR PUMPS:
----------

Keep away from cheap pumps.  Make sure they are UL listed (as you
should with all other electrical devices you are planning to use
with your aquarium).  Listen to the pump before you buy it.  If you
can hear it in the noisy petshop, imagine what it will sound like
in your silent house at 2 AM.  It is also a good idea to get a pump
that is not too much more powerful than you need - more powerful
pumps are invariably more noisy.

As a general rule, "adjustable" air pumps are worth extra money
only if the adjustment is electronic, rather than by a by-pass
valve.  The former is more quiet.  Make sure your pump is
positioned above the water level of your tank, because power
failures and other events can cause water to back-siphon into the
pump and flood it.  You can also use "check-valves" available at
pet shops to make certain that this does not happen.

The following is from Spass Stoiantschewsky:

spass@midas.wr.tek.com

and the last name is spelled "stoiantschewsky", my system
has it spelled wrong...always has, probably always will...

the address will probably change, but i haven't the faintest
idea when...it should have already changed...

best pump tested at depth to date: tetra luft g 
best pump volume (shallow depth) to date: whisper 1000
noisiest pumps: whisper
quietest pumps: challenger (?), followed closely by tetra and
silencer.

best buy in pumps: tetra luft g

noise level measurements are purely by ear.

i'd like to talk to people who have pumps they particularly like 
or dislike and anyone who has pumps that haven't been tested (easy
test).
untested pumps: schego, iwaki, wisa, supra 
tested pumps: whisper, silencer, tetra, challenger

[Ed. Note.  Spass will post a more complete article soon. ]

Disclaimer:
-----------
Some answers listed above may reflect personal biases of the author
and the FAQ's contributors.  In cases where the answers name
specific products and their respective manufacturers, these are not
to be taken as endorsements, nor commercials for the manufacturer. 
Where cost information is stated (magazine subscription rates),
this is based on "street" information, and are in no way binding on
the publisher.  The answers contained in this series pertain to
discussions on the rec. and alt.aquaria newsgroups, and are by no means
exhaustive.  This series is not intended to take the place of good
aquarium books on the subject matter.

Copyright:
----------
The FAQ owes its existence to the contributors of the net, and as
such it belongs to the readers of rec.aquaria and alt.aquaria. 
Copies can be made freely, as long as it is distributed at no
charge, and the disclaimers and the copyright notice are included.

Newsgroups: alt.aquaria,rec.aquaria