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Reef Keeping


Reef Keeping Top ten most costly mistakes If you decide to make a salt water aquarium it can be a little intimidating review 96.5% water 3.5% salt by weight Even ions ... – PowerPoint PPT presentation

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Title: Reef Keeping

Reef Keeping
  • Top ten most costly mistakes

  • If you decide to make a salt water aquarium it
    can be a little intimidating

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  • 96.5 water
  • 3.5 salt by weight
  • Even ions at low concentration are important to
    ocean organisms
  • With the salts comes water changesdensity,
    conductivity, and refractive index

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  • The index of refraction (or refractive index) is
    the ratio of the speed of light traveling through
    a vacuum to the speed of light in the material
    being tested. Most aquarists do not realize that
    when using a refractometer, they are measuring
    the speed of light through their aquarium's
    water, so having such knowledge might be a good
    way to impress friends with your technical

  • Light travels through most materials more slowly
    than it does through a vacuum, so their
    refractive index is higher than 1.00000. The
    detailed mathematics and physics behind
    refractive index are actually quite complicated,
    because it is often a complex number with real
    and imaginary parts, but a simple version is
    adequate for all purposes that a reef aquarist
    would encounter. Some materials slow light
    traveling through them more than others, and
    slower light travel leads to a higher refractive
    index. Table 1 shows some typical refractive
    index values for comparative purposes.

  • Table 1. Index of Refraction of Various
  • Vacuum1.0000
  • Air 1.0003
  • Water (pure)1.3330
  • Seawater (35 ppt)1.3394
  • Ethyl alcohol 1.361
  • Sugar solution (80 sugar)1.49
  • Glass (soda lime)1.510

  • In solutions of two compounds, such as ethyl
    alcohol in water, sugar in water or salt in
    water, the refractive index changes in step with
    how much of each component is present.
  • refractometers are used in brewing, sugar
    refining, analyzing blood and urine protein and
    many other industries where a quick measure of
    refractive index can lead to a good assessment of
    what is present.

  • It cannot tell you what the molecule is but it
    can give you an idea of how much

Price range refractometer100-200 dollars
  • Aquarists can use the effects that added salts
    have on the refractive index of a water solution
    to determine the salinity of reef aquarium water.
    As the salinity of seawater rises, the amount of
    salt added rises, so the refractive index rises.

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  • How well electrons move through the wateror how
    well electricity moves through the water

NaCl density (W / V) Conductivity (mS / cm) NaCl density (W / V) Conductivity (mS / cm)
0.1 2.0 1.1 19.2
0.2 3.9 1.2 20.8
0.3 5.7 1.3 22.4
0.4 7.5 1.4 24.0
0.5 9.2 1.5 25.6
0.6 10.9 1.6 27.1
0.7 12.6 1.7 28.6
0.8 14.3 1.8 30.1
0.9 16.0 1.9 31.6
1.0 17.6 2.0 33.0
  • Refractive index, conductivity, and density can
    all be used by someone keeping a reef (aquarium)
    to test for salinity.

90-600 dollars
4 Main Ions
  • Chloride
  • Sodium
  • Sulfate
  • magnesium

Natural Seawater for a reef
  • Collect it yourself but important factors how
    pure it was at collection and how pure it
    remained until use.
  • Collect the water offshore to avoid runoff
  • Or collect from a rising tide
  • Coastal waters have a lot of chemicals and

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  • If natural seawater is stored too long and it
    stagnates ...the break down of organic molecules
    can produce toxic substances.
  • It is better to use immediately

Artificial Seawater
  • It is probably ok just to use the cheapest you
    can get in a salt mix for an aquarium
  • Do not use sea salt for cooking it is usually to
    low in magnesium
  • It is hard to match the concentration of the less
    common ions in a salt mix
  • Everyone has their own opinion about which salt
    mix is best

Prices range 25-115 dollars
  • In order to add the most common ions to water
  • It takes a lot of material. Unless they are in
    pure (very expensive) form they will put a lot of
    impurities in the water.

  • To be honest, the evidence for using one salt mix
    over another is marginal at best.  Certainly some
    are better, and some may be bad, but no simple
    ranking can be made.  Every artificial salt mix
    varies from natural seawater's concentrations of
    some ions. 
  • many that claim to try to match seawater
    actually do a surprisingly poor job, and differ

  • More expensive salt mixes can theoretically do a
    better job by purchasing purer raw materials, but
    that does not ensure that those companies do so.

  • matching natural seawater, is the problem. None
    really does, and it becomes very difficult to
    decide what is best. 
  • For example, is it better to have too much
    sulfate or too little fluoride? 
  • Too much strontium or too little potassium?  No
    one knows.  Ask that question about nearly every
    chemical constituent, and the true answer is, No
    one knows

So which to use
  • It is probably best to ask people that have made
    successful tanks beforeIn a poll I have taken 9
    people used instant ocean and 7 used Reef
    Crystals and the rest were divided up into 1
    person each with a different brand

Pure Water
  • In addition to using a suitable salt mix, it is
    important to use suitably pure freshwater, both
    for making salt mixes and for topping-off for
    evaporative losses.   .

  • The majority of experienced and successful reef
    aquarists in the U.S. appear to use RO/DI
    (reverse osmosis/deionization) to purify tap

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Prices range 100-300 dollars
  • Reverse osmosis (RO) alone may be adequate in
    some cases, but not always.

  • The use of tap water itself entails a number of
    concerns besides the presence of chlorine. 
  • First is Chloramines which does not dissipate
    after sitting around, the way many aquarists have
    done in the past for chlorine.  It is now being
    added to many water supplies, and is much longer
    lived than chlorine. 
  • It also requires special treatments, not just the
    standard dechlorinating agents.  Other concerns
    with tap water are copper (which often comes from
    your home's plumbing), nutrients (nitrate and
    phosphate) and alkalinity (which is not per se a
    problem, but can boost levels too high in some
    cases). .

  • Chloramines can be removed by means of a granular
    active carbon filter

  • Chloramine (monochloramine) is a chemical
    compound with the formula NH2Cl. It is usually
    used as a dilute solution where it is used as a
  • Chlorine combines with ammonia

  • In general, I recommend avoiding tap water. 
    Sure, some folks use it and have fine
    aquaria. Just safer in the long run.

  • Typical commercial distilled water is likely
    acceptable, as long as it has not been exposed to
    metals such as copper in condensers, pipes or
    holding tanks.  Unfortunately, it is not easy to
    know the production history of distilled water,
    and testing with most copper test kits may be
    inadequate because they may not accurately read
    low enough to detect its presence.

  • Many aquarists use water provided by machines at
    grocery stores or from their local fish stores. 
    Many of these are apparently reverse osmosis (RO)

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  • natural ocean water has an average salinity of
    about 35 ppt, corresponding to a specific gravity
    of about 1.0264 and a conductivity of 53 mS/cm. 
    Salinity can vary substantially from place to

  • As far as I know, little real evidence suggests
    that keeping a coral reef aquarium at anything
    other than natural salinity levels is preferable.

  • It appears to be common practice to keep marine
    fish, and in many cases reef aquaria, at somewhat
    lower than natural salinity levels. This practice
    stems, at least in part, from the belief that
    fish are less stressed at reduced salinity.

  • Substantial misunderstandings also arise among
    aquarists as to how specific gravity really
    relates to salinity, especially considering
    temperature effects.

Specific gravity versus slainity
  • One question that every marine aquarist faces is
    the amount of salt to add to the tank. Most
    beginning texts choose to describe the salinity
    in terms of specific gravity, and go on to relate
    how one measures it with a hydrometer. While not
    nearly as precise as measuring salinity with a
    conductivity probe or a refractometer,
    hydrometers are chosen by many because they are
    inexpensive and easy to use.

Hydrometer measures density or specific gravity
  • For many aquarium purposes, they are perfectly

The wonderful world of spcific gravity
  • One question that every marine aquarist faces is
    the amount of salt to add to the tank. Most
    beginning texts choose to describe the salinity
    in terms of specific gravity, and go on to relate
    how one measures it with a hydrometer.

  • While not nearly as precise as measuring salinity
    with a conductivity probe or a refractometer,
    hydrometers are chosen by many because they are
    inexpensive and easy to use. For many aquarium
    purposes, they are perfectly adequate.

  • Why is specific gravity useful to aquarists?
    Primarily because it is a simple and quantitative
    way to tell how much of something is in water. If
    things less dense than water are dissolved in it,
    then the specific gravity will drop. Ethanol, for
    example, is less dense than water, and makes the
    specific gravity drop. This fact is used by
    brewers to gauge the amount of alcohol in their

  • Likewise, if things denser than water are
    dissolved in it, the specific gravity goes up.
    Nearly all inorganic salts are denser than water,
    so dissolving them in water makes the specific
    gravity rise. This rise can be used by aquarists
    to gauge how much salt is in their water. Of
    course, it cannot tell you what is in the water,
    but if you are using an appropriate salt mix, it
    can tell you how much is there and whether it
    approximates natural seawater or not.

  • The salinity on natural reefs has been discussed
    in previous articles. My recommendation is to
    maintain salinity at a natural level. If the
    organisms in the aquarium are from brackish
    environments with lower salinity, or from the Red
    Sea with higher salinity, selecting something
    other than 35 ppt may make good sense. Otherwise,
    I suggest targeting a salinity of 35 ppt
    (specific gravity 1.0264 conductivity 53

  • Fortunately, coral reef aquaria seem rather
    forgiving with respect to salinity.  The range of
    salinities in what most would say are successful
    reef aquaria is actually quite large.  Dont
    agonize over small changes from natural
    seawater.  You will not notice any benefit
    changing from 36 or 34 ppt to 35 ppt (specific
    gravity 1.0256 to 1.0271).  Many fine reef
    aquaria appear to run at salinity levels as low
    as 31 ppt (specific gravity 1.023), but bear in
    mind that the values that aquarists report (as
    well as your own measurements) are fairly likely
    to be inaccurate, so pushing the low or high end
    of the range may not be prudent. 

  • Bear in mind that if aquarists target salinity
    values different than 35 ppt, the amounts of
    calcium, magnesium, alkalinity, etc., will all
    likely deviate from natural levels as well.  For
    example, making artificial seawater to a low
    salinity will normally result in low values for
    these parameters and may require adjustments.

How to Mix Artificial Seawater
  • First, add the freshwater to the mixing
    container.  The container can be any size, but
    larger containers will be less likely to have
    off parameters caused by taking a small portion
    of a container of salt mix that may not be
    representative of the bucket or bag due to

  • I make up 88 gallons at a time.  Assuming that it
    is made from pure freshwater, mixed artificial
    seawater can be stored for as long as needed
    without continuous stirring or heating.  I keep
    mine for a few weeks completely unstirred after
    initial mixing.  It will not become anaerobic
    (although used tank water or natural seawater may
    become anaerobic due to the breakdown of organics
    in it, and should not be stored unaerated).

  • Do not add anything other than salt mix to the
    freshwater unless you determine, after mixing in
    the salt, that it is deficient in something
    important.  Add the salt and stir. Adding the
    salt before the water can be okay, but causes an
    unusually high salinity for the period when you
    are adding water, which can result in the
    formation of certain precipitates that may be
    hard to redissolve.

  • Overnight stirring with a powerhead is a good way
    to dissolve the salt, but shorter stirring can be
    okay, if done vigorously.  If you are using the
    saltwater for very small water changes (2 or
    less at once), you need not heat it.  If you want
    to add any calcium (I do), magnesium (I do),
    alkalinity (I dont) or anything else (not
    recommended), add it after the salt has
    dissolved.  The overnight stirring will also help
    with aeration, which can be useful for some mixes
    that start with a high pH and need to pull in CO2
    from the air to reach normal pH. 

  • After aeration, the pH is determined only by the
    alkalinity and the ambient carbon dioxide level
    in the air.  It is not an attribute of the salt
    mix.  More details on pH will be covered in a
    future article.  Aeration also pulls in oxygen,
    if the starting freshwater was deficient in

  • Measure the salinity, and then adjust it by
    adding more salt mix or more water as necessary
    to reach your desired salinity.

  • he following guidelines provide a short synopsis
    of the important conclusions from this article
  • 1.  Dont focus on perfect salt mixes (none
    exist), or any other chemical attribute of coral
    reef aquaria.  Focus on attainable suitability.
  • 2.  Natural seawater might be a fine choice for a
    coral reef aquarium.  If using natural seawater,
    be sure it is collected, treated and stored in a
    suitable manner.

  • 3.  Artificial seawater is another option.  Dont
    get worked up by every salt mix comparison that
    comes along. 

  • A variety of brands of salt mix have been used
    successfully by a large number of aquarists,
    including Reef Crystals, Instant Ocean and Tropic
    Marin (Pro and regular).  If you select one of
    these, it is unlikely that any failures you will
    encounter will relate to a problem with the salt

  • 4.  Use appropriately pure freshwater to make the
    salt mix and top-off for evaporation.
  • 5.  Use an appropriate device, appropriately
    calibrated, to measure salinity.  I recommend
    targeting natural ocean salinity (S35 PSU or 35
    ppt, specific gravity 1.0264).  But salinity is
    fairly forgiving, and a range around these values
    is certainly acceptable.

  • Good water need not require an overly
    complicated exploration of chemical and
    biological testing.  Asking questions from
    experienced people is the best bet.   Using that
    type of information, this article provides the
    basics necessary to obtain suitable aquarium
    water to start with.
  • Of course, that water quickly becomes depleted in
    some chemicals, and polluted with others. 
    Subsequent articles in this series will provide
    details on how to deal with those issues in ways
    that are tried and true, and not overly