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Archive-name: aquaria/general-faq/water
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			       Water Quality

Rev 1.23 9/3/94

Prologue:
---------
This monthly series is intended to address some of the frequently
asked questions (FAQ) on the rec., alt., and sci.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.  Please see the file README for pointers to
other topics.

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.


WATER QUALITY, NITROGEN CYCLE AND FISH DISEASE PREVENTION:
----------------------------------------------------------
     Water quality is important to the health of your piscine
guests.  In fact, most diseases and parasitic infections are due to
lowered immunal defenses because of poor nutrition and bad water
quality.  So, if your fish are diseased, the first suspect is
usually your water.
     In the wild, most fish live in large bodies of water that
minimizes the changes in water quality.  (i.e. the ocean remains
very constant in salinity, temperature, etc. because it is so
large.  Therefore, marine aquaria require constant vigilant
care).  So depending on the fish, the constancy of the water
quality is also important.

WATER QUALITY
     Besides the nitrogen cycle and the disposal of organic waste,
there are other factors that influence water quality.  Air pumps
can draw contaminated air (read smoker exhalations) into the water. 
Other pollutants include paint, insecticides etc.  Therefore air
should be filtered before being pumped into the water.  (See
FILTERS).  Another major form of contaminants are our hands.  If we
do not wash our hands, we carry Lord-knows-what into the water (do
you know where your hands have been?).  If we wash them, we bring
minute traces of soap which is very bad for the mucous on the fish. 
The best thing is to rinse our hands in very hot water.

NITROGEN CYCLE
     Ecosystems absorb and make use of the biological/metabolic
waste.  The waste (pee and poo) from animals breaks down into
ammonia and other nitrogen compounds which are used by other
organisms (such as plants) in the ecosystem.
     Ammonia (NH3) and ammonium (NH4+) exist in equilibrium with
the exact ratios depending on pH (higher pH allows for more
ammonia).  Ammonia is poisonous to fish in just about any
concentration (ammonium is relatively harmless).  It is converted
by bacteria of Nitrosomonas species (among others) to nitrite,
which is also toxic (but less so).  Nitrite, in turn, is converted
to relatively harmless nitrate by the bacteria of Nitrobacter
species (among others).  This is where things usually stop in an
aquarium.
     Despite the mistaken notion promoted by all too many aquarium
books, nitrates are not readily taken up by the plants and actually
stop the plants' growth in high concentrations.  There are two ways
to get rid of the nitrates (which become stressful for fish above
60 ppm concentrations): partial water changes and denitrification. 
The former is the easiest and least expensive method.  The latter
can be done by using bacteria of Pseudomonas species living in
nearly anaerobic conditions in very slow flow and long-path filters
or by ion-exchange (see Chemical Filtration).  Both are not at all
cheap or very easy to tune.  So stick to partial water changes. 
     Plants are somewhat useful in the nitrogen cycle.  It is now
believed that they absorb ammonium and in doing so, they shunt the
nitrogen cycle by shifting the ammonia/ammonium balance.  This in
turn causes more ammonia to be converted to ammonium to maintain
the balance at a specific pH.  But because a large number of plants
are needed (most fish concentrations in the wild are much lower
than that found in aquaria), one should stick with water changes.

 [The preceding is a generalization.  The real bio-chemistry of the
nitrogen cycle and all its aspects is very complex.  And, of
course, all of this is irrelevant to well-tuned salt-water reef
tanks].

NOTES ON NITROGEN TESTS  (Dustin Laurence, laurence@alice.caltech.edu)

Tests for nitrogen compounds (ammonia or NH3, nitrite or NH2--, and nitrate
or NH3-) measure the substance in question on one of two scales; ion
concentration or nitrogen-ion concentration.  Concentration is generally
expressed in ppm (parts per million).  Ion concentration is then written as
ppm NH3, ppm NO2--, or ppm NO3-, and nitrogen-ion concentration is written
as ppm N-NH3, ppm N-NO2--, or ppm N-NO3-.  (When these symbols are typeset
in a book or instruction sheet, the number are written as subscripts below
the letters and the minus signs which follow NO2 and NO3 are written as
superscripts; the charges (minus signs) are often omitted entirely.)

The difference between these measures is not difficult to understand, but it
can cause a lot of confusion because it is often not obvious which measure
that a particular author or test kit refers to.  First, the bottom line for
those who don't want to know the details:

  [N-NH3] (ammonia-nitrogen) = 0.8 [NH3] (ammonia ion)
                             or
                       [NH3] = 1.3 [N-NH3]


[N-NO2--] (nitrite-nitrogen) = 0.3 [NO2--] (nitrite ion)
                             or
                     [NO2--] = 3.3[N-NO2--]


 [N-NO3-] (nitrate-nitrogen) = 0.23 [NO3-] (nitrate ion)
                             or
                      [NO3-] = 4.4 [N-NO3-]

Where [] indicates concentration in parts per million (ppm).

Ammonia and nitrite concentrations should be too low to measure with hobby
equipment in a cycled aquarium, so the distinction between the two measures
is rarely useful to the amateur hobbyist; 1.3 times zero is still zero!
However, nitrate concentrations will in general not only be nonzero but
increase over time, and it is important for the aquarist to monitor their
levels as necessary and to know what levels are acceptable for her tank.
Therefore, you can usually buy relatively cheap ammonia and nitrite kits and
spend more on a good nitrate kit.

One general rule of thumb is never buy a kit that asks you to compare the
color of a clear liquid to a color on an opaque chart; comparisons of colors
of vastly different optical depths are very hard to estimate.  Good kits
give you a colored transparency for the comparison.

You can't trust the zero of many kits!  Do a test on distilled, reverse
osmosis, or de-ionized water; often you will get a false reading.  Subtract
this reading from each test of your aquarium water for a somewhat better
estimate of what the true levels are.

Most aquarium authors give recommendations for acceptable nitrate levels in
terms of nitrate ion concentrations.  Recommendations for marine tanks range
from 10 to 40ppm nitrate ion for fish-only tanks and <5 to 10ppm nitrate ion
for reef systems, though many fish-only tanks run at much higher levels
(sometimes with no ill effects, and sometimes...).  On the other hand, many
tests read in terms of nitrogen-ion concentrations, since this measure is
more commonly used by professionals.  Trouble often occurs when the hobbyist
measures her nitrate levels in nitrogen-ion concentrations and unwarily
compares the resulting number with a recommendation in ion concentrations,
possibly resulting in nitrate concentrations up to four times that intended.

If a nitrate test does not mention which scale is being used, it may be
possible to determine this by testing an established, well maintained tank.
However, someone who has access to a well maintained tank usually already
knows the scale of his favorite test, and most often it is the person who
is trying to set up a tank for the first time that needs this information.
A list of common tests and their measure is included at the end of this
section as well.

If you absolutely must use a test that does not mention the scale, it is best
to be safe and assume nitrogen-ion concentration.  However, one may
legitimately question the likely quality of a test which does not provide
this information, and a move to a better test is probably indicated.

Now the details: the measure of concentration used on both scales is parts
per million, abbreviated ppm, which means: units of mass of the measured
substance per million units of mass of the final solution. (For aquarist's
purposes, this is identical to milligrams per liter, or mg/l; one liter of
fresh water is almost exactly one kilogram, and a liter of salt water is
only a couple of percent more.)

On the ion scale we measure the mass of the complete ion which makes up the
substance, while in the nitrogen-ion scale we only measure the mass of the
nitrogen atom in that ion.  The first scale measures the concentration of
nitrate ions, while the second measures the concentration of nitrogen in
the form of nitrate.  In fact, it could be called the "nitrogen as nitrate"
scale.

Which scale is more natural depends on one's intent.  Most aquarists are
interested in the toxicity of, say, nitrate ions in aquarium water, in
which case the ion scale is the most natural; it directly measures the
amount of the toxic ion present.  On the other hand, a biologist may be
studying the nitrogen cycle in a particular system, and would thus be
interested in measuring the total amount of inorganic nitrogenous wastes
present in a water sample.  Then the nitrogen-ion scale is most natural,
since the concentrations can be added directly.  One could not add the ion
concentrations for this purpose; this would be exactly like adding apples
and oranges.

The conversions between the scales is easily derived as follows:

        mass of the complete ion
[ion] = ------------------------ [nitrogen-ion]
        mass of a nitrogen atom

And clearly 1 over this conversion factor is used when converting ion
concentration to nitrogen-ion concentration.  The interested reader can
reproduce the above numbers with this formula and the following information.

Masses:

To within a percent, we can use mass of a hydrogen atom (H) = 1, mass of a
nitrogen atom (N) = 14, and mass of an oxygen atom (O) = 16.

Chemical Species  Formula  Mass

Nitrate ion       NO3-     14+3*16=62
Nitrite ion       NO2--    14+2*16=46
Ammonium ion      NH4+      14+4*1=18
Ammonia molecule  NH3       14+3*1=17

The calculation for the ammonia conversion factor is complicated by the fact
that in solution ammonia exists in two forms.  In a given sample of water,
part of the ammonia will be in the form of ammonia (NH3) and part in the form
of ammonium ions (NH4+).  Further, the ratio of ammonia to ammonium is pH
dependent.  However, even if we assume that the ammonia present is all in
one form or the other, the difference between the resulting numbers is not
significant for our purposes (1.21 vs 1.29).

The commonly quoted figure of 1.3 probably results from the fact that if
the ratio of the two species was exactly 50%, the conversion factor would
be exactly 1.25.  Since at the pH of most aquaria more of the ions are
ammonium than ammonia,  the conversion factor must be more than 1.25 and
so we round to 1.3.  [This last sentence is a guess on my part, since I
don't really know what the pH of the average freshwater aquarium is.  It
should be true for all marine aquaria.]

The following is an (incomplete) list of common tests, the measure used
by each, and comments be various people on the net.

DryTab                      ion

    From Dustin Laurence:

        These kits are IMHO almost completely worthless.  Buy something
        like the SeaTest kits instead for good, fairly inexpensive tests.

Dupla                       ion?

    From Ken Koellner:

        English instructions are translated from the German with European
        conventions intact.  American aquarists beware things like 0,2
        for 0.2 .

HACH Saltwatermaster kit    nitrogen-ion

    From Mike Loughlin:

        Designed for aquaculture, sensitive to low concentrations.  Excellent
        technical support.  Cost: $35.75 in the 1992 catalog.

HATCH low range nitrate     nitrogen-ion

    From Greg Smith:

        Range: 0-1ppm N-NO3 in .02 increments.  Smallest readable
        increment: .02ppm.  Cost: ~55.  Comments: repeatable, consistent, kit
        uses colorwheel.  This is the best kit I have used, better than
        lamotte, seatest, kordon.  Number of tests: (30, 50? not sure).

    Keith Rogers Adds:

        Note that you get erroneous results in salt water unless you get the
        proper SW version of NitraVer 6 (one of the reagents used).  They will
        *not* substitute the SW reagent in place of the FW one.  So, if you
        need the kit for SW you also need to buy the other reagent for an
        extra $18.50.  Shipping cost is $8.  The up side to this is you get a
        FW and SW nitrate kit which is better than all the rest bar none.

Kordon low range nitrate    nitrogen

    From Greg Smith:

        Range: 0-55ppm NO3.  Smallest readable increment: 5ppm.  Cost ~10.
        Number of tests: (10 or 20 not sure).  Comments: good kit.

Lamotte                     nitrogen-ion?

SeaTest                     nitrogen-ion

    From Dustin Laurence:

        Good kits for average aquarists.  Reef aquarists will want a better
        (and more expensive!) nitrate kit after their reef has matured.

    From Ray Wallace (on nitrate kit):

        Range: 0-12 mg/L (ppm) and 0-100 mg/L (ppm) Nitrate-Nitrogen (NO3-N)
        scales.  Uses a slide with gradual color scales.  Smallest numbered
        increment is 1.2.  25 tests using premeasured powder in packets.

PRACTICAL FRESHWATER HARDNESS

  Water hardness is of interest to aquarists for two reasons: to
provide the proper environment for the fish and to help stabilize the
pH in the aquarium.  There are two types of water hardness: general
hardness (GH) and carbonate hardness (KH).  A third term commonly used
is total hardness which is a combination of GH and KH.  Since it is
important to know both the GH and KH, the use of total hardness can be
misleading and should be avoided.

GENERAL HARDNESS 

  General hardness is primarily the measure of calcium (Ca++) and
magnesium (Mg++) ions in the water.  Other ions can contribute to GH
but their effects are usually insignificant and the other ions are
difficult to measure.  GH will not directly affect pH although "hard"
water is generally alkaline due to some interaction of GH and KH.

  GH is commonly expressed in parts per million (ppm) of calcium
carbonate (CaCO3), degrees hardness (dH) or, more properly, the molar
concentration of CaCO3.  One German degree hardness (dH) is 10 mg of
calcium oxide (CaO) per liter.  In the U.S., hardness is usually
measured in ppm of CaCO3.  A German dH is 17.8 ppm CaCO3.  A molar
concentration of 1 milliequivalent per liter (mEq/l) = 2.8 dH = 50
ppm.  Note that most test kits give the hardness in units of CaCO3;
this means the hardness is equivalent to that much CaCO3 in water but
does not mean it actually came from CaCO3.  Water hardness follows
these guidelines:

      0 -  4 dH,    0 -   70 ppm : very soft
      4 -  8 dH,   70 -  140 ppm : soft
      8 - 12 dH,  140 -  210 ppm : medium hard 
     12 - 18 dH,  210 -  320 ppm : fairly hard
     18 - 30 dH,  320 -  530 ppm : hard
     higher : liquid rock (Lake Malawi and Los Angeles, CA)

  General hardness is the more important of the two in biological
processes.  When a fish or plant is said to prefer "hard" or "soft"
water, this is referring to GH.  Incorrect GH will affect the transfer
of nutrients and waste products through cell membranes and can affect
egg fertility, proper functioning of internal organs such as kidneys
and growth.  Within reason, most fish and plants can successfully
adapt to local GH conditions, although breeding may be impaired.

CARBONATE HARDNESS

  Carbonate hardness (KH) is the measure of bicarbonate (HCO3-) and
carbonate (CO3--) ions in the water.  In freshwater aquariums of
neutral pH, bicarbonate ions predominate and in saltwater aquariums,
carbonate ions begin to play a role.  Alkalinity is the measure of the
total acid binding capacity (all the anions which can bind with free
H+) but is comprised mostly of carbonate hardness in freshwater
systems.  Thus, in practical freshwater usage, the terms carbonate
hardness, acid binding, acid buffering capacity and alkalinity are
used interchangeably.  In an aquarium, KH acts as a chemical buffering
agent, helping to stabilize pH.  KH is generally referred to in degrees
hardness and is expressed in CaCO3 equivalents just like GH.

  In simple terms, pH is determined by the negative log of the
concentration of free hydrogen ions (H+) in the water.  If you add a
strong acid such as nitric acid to water, it completely dissociates
into hydrogen ions (H+) and its "conjugate base" or "salt", NO3- or
nitrate.  The hydrogen ions freed in the reaction then increase the
concentration of hydrogen ions and reduce the pH.  Since nitric acid
is the end product of the nitrogen cycle, this explains why aquarium
pH tends to decrease and nitrates tend to increase over time.

  When the aquarium has some carbonate buffering in it, the
bicarbonate ions will combine with the excess hydrogen ions to form
carbonic acid (H2CO3) which then slowly breaks down into CO2 and
water.  Since the excess hydrogen ions are used in the reaction, the
pH does not change very much.  Over time, as the carbonate ions are
used up, the buffering capacity will drop and larger pH changes will
be noted.  From this it is clear why aquariums with low KH seem
unstable - as acid is produced by biological action, the KH is used
up; when it is gone, the pH is free to drop rapidly as H+ ions are
generated.

ADJUSTING FRESHWATER HARDNESS

  If your local water is too hard for the fish and plants you desire,
it can be softened.  There are many ways to do this but some are more
suited to aquarium use than others.  The best (and most expensive, of
course) is to use a reverse osmosis (RO) deionizer and mix the
resulting water (GH=0) with tap water to get the desired GH.  Peat
moss can be used to soften and condition the water for use in South
American cichlid tanks, but will add a slight tea color to the water.
Peat filtering may be difficult to control.  Peat should be boiled
first to kill any unwanted organisms. 

  Commercial water softening resin "pillows" can be used on a small
scale, but are not effective for larger amounts of water.  Water
softening systems designed for large scale home use (like bath water)
are not suitable since they use an ion exchange principle: usually
sodium ions are substituted for calcium and magnesium ions and excess
sodium is not desired in the aquarium.  An even worse practice is to
use a cation exchange resin in the hydrogen ion form and use it to
pull divalent ions out of the water.

  If the local GH is too low, it can be raised by adding calcium
sulfate and/or magnesium sulfate.  This has the drawback of
introducing sulfates (SO4--) into the water, so care should be
exercised.  Calcium carbonate can be used, but it will also raise the
KH (this is ideal for the lucky few who have naturally soft water).
Various combinations can be used to produce the desired results.

  Carbonate hardness can be reduced by boiling the water (impractical
for all but the smallest aquariums; let it cool before adding to the
tank :-) or by peat filtering.

  Carbonate hardness can be easily increased by adding sodium
bicarbonate.  Calcium carbonate will increase both KH and GH in equal
parts.

  One teaspoon (about 6 grams) of sodium bicarbonate (NaHCO3) per 50
liters of water will increase KH by 4 degrees and will not increase
general hardness.  Two teaspoons (about 4 grams) of calcium carbonate
(CaCO3) per 50 liters of water will increase both KH and GH by 4
degrees.  Different proportions of each can be used to get the correct
KH/GH balance dictated by the fish and plants in the tank.  Since it
is difficult to accurately measure small quantities of dry chemicals
at home, a test kit should be used to verify the actual KH and GH that
is achieved.


FRESHWATER CHEMISTRY DETAILS

  In more detail, the pH of a buffered solution can be expressed by the
Henderson-Hasselbach equation:

                base
  pH = pK + log ----  
                acid

where pK is one or more "equilibrium dissociation constants" of the
weak acid.  In the bicarbonate and carbonate buffering cases, this is:

                  HCO3-                            CO3--
  pH = 6.37 + log -----    and    pH = 10.25 + log -----          
                  H2CO3                            HCO3-
  
Note that the pK values are affected rather appreciably by temperature
and chlorinity.  If you plot the pH versus the ratio of base to acid,
you will get a logarithmic graph something like this:

 100% base             ,---------      ,----------
                      /               /
              H2CO3  |     HCO3-     |      CO3--
  50% mix     + CO2  |<- pH=6.37     |<- pH=10.25
                     |               |
                     /               /    
 100% acid  --------`       --------`    

       pH   ...5...6...7...8...9...10..11..12...

Bicarbonate buffering is effective over ratios from 1:100 up to
100:1.  This gives an effective pH range of 4.37 to 8.37, which, not
coincidently, defines the pH range of most aquatic life.
 
  If you add bicarbonate ions (for example, by adding sodium
bicarbonate or calcium carbonate), the base to acid ratio will
increase and the pH will increase.  From the graph, the rate of
increase will be determined by the pH you started with: at pH = 6.37,
you will need a lot of bicarbonate ions to change the pH; at pH=7.5,
you will need a lot less.  (Note: the chemical equilibria of the
various components of the carbonate system (CO2, H2CO3, HCO3- and
CO3--) are very complex and are beyond the capability of the author to
fully describe).

  The rise in pH that occurs when KH is added will be balanced to a
degree by the dissolved CO2 in the water.  Fortunately, CO2 is also a
result of the nitrification process and fish and plant respiration so
it is readily available.  The CO2 will form small amounts of carbonic
acid and bicarbonate which will tend to reduce the pH.  This mechanism
gives us a way to regulate pH in the aquarium.

  If the pH of an aquarium is determined PRIMARILY by the carbonate
buffering system, then the relation of pH and KH and dissolved CO2 is
fixed.  You can change either KH or CO2 to set the pH.  An automatic CO2
injection system will measure pH and inject CO2 to lower it if it
exceeds a set point.  In this case KH is fixed.  As the CO2 is used by
plants and diffuses into the atmosphere, the pH will rise.  The
controller cycles the CO2 on and off to keep the pH around a fixed
value.

  The following chart shows dissolved CO2 levels in ppm for a range of
KH and pH values:

                 degrees KH
            2    3    4    5    6
         +------------------------
     6.6 | 15   23   30   38   46
     6.7 | 12   18   24   30   36
     6.8 |  9   14   19   24   28
 pH  6.9 |  7   12   15   19   23
     7.0 |  6    9   12   15   18
     7.1 |  5    7    9   12   14
     7.2 |  4    6    8    9   11
     7.3 |  3    4    6    7    9
     7.4 | 2.4   3    5    6    7
     7.5 | 1.9  2.5  3.5   5    5
     7.6 | 1.5   2   2.5   3    4
     7.7 |  1   1.5   2   2.5   3
     7.8 | 0.9  1.1  1.5   2    2
     7.9 | 0.6  0.9   1   1.2  1.6
     8.0 | 0.5  0.7  0.9   1   1.2

Note that typical dissolved CO2 levels in a moderately stocked
aquarium will be in the range of 2-3 ppm.  From the chart, it is clear
that almost any carbonate hardness will produce a pH in the mid 7
range unless extra CO2 is added.  For a typical planted aquarium,
pH=6.9, KH=4 and CO2=15 ppm is just about ideal.

PRACTICAL SALTWATER HARDNESS (to be written!)

FISH DISEASE PREVENTION
     Nutrition, water quality, and sanitary practices should
prevent most diseases.  Healthy fish have a way of fending off
attacks.
     Good sanitary practices include: not pouring pet store water
into an established tank, not buying diseased fish , not using the
same net between aquaria without first rinsing, and storing the
net in a clean, non-dusty place.
     Many times, live food are the most nutritious (for fish that
are meat eaters), but carry with them a danger of parasites and
disease.  Most notable are live tubifex worms (collected from
sewers and other nasty habitats; buy the freeze-dried variety),
goldfish (these are often sick by the time they are in the store),
pond collected daphnia etc.  One should always inspect the food
before offering it to the fish.

WHEN FISH ARE SICK
     When your fish are sick, you can post for diagnoses 
(Consultation of a fish book is probably preferred).  Please
include as much information as you can gather.

1.   Describe the condition of the fish with any externally visible
     growths, symptoms, behavioral modifications etc.  Also, post
     the length of time this has been going on.
2.   Describe the aquarium setup.  How big is the aquarium, how
     many fish, what kinds and how large?  How frequent are water
     changes performed?  Lighting and lack of?
3.   Test the water and post pH, temperature and possible
     fluctuations, color, smell.  (taste? :-)
4.   If you have the kits, test and post the ammonium, nitrite,
     nitrate and hardness levels.
5.   Describe medication already used, and the after effects.

     Some medication companies (such as Mardel) print a diagnoses
chart and include this with the medicine.  Of course they recommend
their own brands as a cure for everything.  Find out the disease
and consult the net for recommendations.
     Many people recommend a hospital tank for isolating sick fish. 
The smaller hospital setup has the added benefit of minimizing the
amount of medicine used.  If hospital tanks are not left constantly
running, and are stored away, starting up one of these will be the
equivalent of starting a new aquarium.  A biological filtration
will need to be started, or seeded from the old filters.  (Some
types of treatment makes this irrelevant since the medicine will
kill all the beneficial bacteria).


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.