As far as making one's own solutions of the most common
elements in the marine aquarium, I can only say it is a
worthwhile effort. It does not take a genius or any special
skills. One only needs an accurate scale, liquid measuring
container and water. It is best to use distilled, or at the very
least RO, water for this endeavor though.
Following are the "cook book recipes" for several
elements. I will give general dosages for the elements, but
remember that without accurately testing
for them and just adding indiscriminately, a lot more harm can be
done than good. Calcium,
strontium, magnesium and bicarbonate all are in a balance with
each other. In other words affecting the concentration of one
will affect the concentration of the other. Indiscriminately
adding one element without balancing it out with the other will
wreak havoc on the system.
Also, I cannot take any responsibility
for what might happen if you decide to make your own
solutions. Chemical impurities, inexact weights and improper
administration of the solutions can all cause disasters. But if
you use good compounds, are tediously careful in the preparation,
and administer, observe and test carefully, lots of satisfaction
can be achieved by preparing one's own additives. Not to mention
the savings that are possible compared to purchasing commercial
products.
Where can the chemical substances be
obtained? Local scientific warehouses and mail order
companies are two possibilities. A search of the Internet will
result in several companies specializing in these substances. Fisher Scientific, Aldrich,
and Alfa Aesar
are some of the better-known ones.
Calcium: Ca; Ca2+ (ion); 40.08 (weight); 400 - 450 ppm (desired concentration)
Bicarbonate: HCO3-
(ion); 61.0172 (weight)
The need for calcium in the marine aquarium is not in
question. Hard corals utilize calcium in form of calcium
carbonate in their skeletons. Soft corals, other invertebrates
and fish need calcium for a number of biochemical processes.
What is in question these days is how to add the calcium. It
can be added to the system in various forms and in several
different ways. Adding Kalkwasser
(Calcium Hydroxide -- Ca(OH)2) is an old and
widespread method pioneered by Peter Wilkens. Opinions vary
whether using Kalkwasser as the main source of calcium is
prudent. A somewhat newer method of adding calcium is with calcium chloride
(CaCl2) on its own. This method has the problem that
when used alone, it creates an ionic imbalance by skewing the
chloride ion concentration. The newest two-part
additives compensate for this by adding
sodium bicarbonate in balanced proportions. One can get around
additives completely by using a kalk reactor. Personally I have
had good luck with dripping Kalkwasser as my make up water (at
night) and adjusting the calcium with calcium chloride.
Calcium (and strontium) is used in the form of its bicarbonate salt by marine organisms.
These are then the ions that we naturally want to have available
in our aquariums as the building blocks for this salt. This is a
further advantage of the "two-part additives," as they
raise the concentration of bicarbonate as well as calcium. Following
is an illustration of how these additives work:
CaCl2 + 2NaHCO3
<==> Ca(HCO3)2 + 2NaCl
Or in other words, calcium chloride plus two (2) sodium
bicarbonates react to calcium bicarbonate plus two (2) sodium
chlorides. This reaction runs in both directions of course. It is
evident though that by adding the compounds in this manner that the sodium and the chloride ions are
balanced out. One only has to monitor the total salinity of the system
and make adjustments accordingly. One also has to add other trace elements in their
proportionate concentrations. This can be done with a good
commercial trace element additive.
In Germany NaCl-free salts are
also now available and can be used with this method. I am not
aware of any NaCl-free salt for sale in the USA yet, but as
interest in this method rises, I would say that it is only a
matter of time before they can be purchased.
Martin Moe describes in his book, The Marine Aquarium
Handbook, how to prepare a synthetic sea salt. If NaCl is left
out of the mixture, a NaCl-free salt could be prepared. He calls
for:
Sodium chloride 23.477g
Magnesium chloride 4.981g
Sodium sulfate 3.917g
Calcium chloride 1.102g
Potassium chloride 0.664g
Sodium bicarbonate 0.192g
Potassium bromide 0.096g
Boric acid 0.026g
Strontium chloride 0.024g
Sodium fluoride 0.003g
Commercial trace elements
This is the amount of salt normally used for 1 liter of water.
Larger amounts would be needed. Multiplying the amounts by 100 or
1000 would make up sufficient salt mixture, and be easier to
measure out as well.
Note: As can later be seen, the prepared solutions will
not add twice as much sodium bicarbonate as calcium chloride. I
can only surmise that Mr. Balling has good reasoning for this.
One reason could be that chloride ions react with any number of
other ions in the system. Another could be that too much
bicarbonate will lower the pH over time. Bicarbonate is of course
part of any good marine buffer, but lowers the pH to around 7.8
if not used in conjunction with borates and carbonates.
Bicarbonates are also added in the third solution (NaCl-free salt
solution) and must be accounted for.
(According to Hans Werner Balling)
375g of calcium chloride (anhydrous) is dissolved in 5000ml of water.
325g of sodium bicarbonate (baking soda) is dissolved in 5000ml of water.
150g of NaCl-free marine salt is
dissolved in 5000ml of water.
These solutions are to be kept in separate containers and are
stabile. If they were to be mixed, calcium carbonate would fall
out and be useless in the aquarium.
Dosage: Initially add
30ml of each solution per 100 liters (approximately 25 gallons)
of water, daily. Continue this until a carbonate hardness of 9 -
11 dH is reached. 30ml once or twice a week, per 100 liters
should then suffice as a maintenance dose.
Carefully observe the animals and watch for any cramping. Test
for calcium and adjust until a concentration of 400 - 450 ppm is
achieved. While large pH swings are avoided with this method,
testing is none the less essential. Large amounts of bicarbonate
are added to the system but no borates or carbonates. A good commercial buffer will still be
necessary to have on hand.
The CaCl2 solution is 0.68 molar (moles per liter).
The NaHCO3 solution is 0.77 molar.
1 mole of CaCl2 = 110.986g
1 mole of NaHCO3 = 84.007g
Determine the exact amount of water in the system. This is of course very difficult to do. Most people estimate how much water is in their system after adding rock, sand, etc. Subtract 10 - 30% of the total volume, depending on the amount of rock, etc. in the system. Do not forget to add the volume of water in the sump back in.
Determine the amount of calcium in the water. This is done with an accurate test kit.
Calculate how much calcium needs to be added to the system to reach the desired concentration.
Calculate how much calcium chloride solution this corresponds to.
Add equal amounts of all the solutions.
Our tank holds 55 gallons of water, has
two inches of sand in the bottom, and rock pyramiding up the
entire back wall. Furthermore the sump contains an additional 10
gallons of water. With the large amount of sand and rock, I would
estimate that there is only about 70% of the volume in the tank
as water. That turns out to be: 55 gallons x 70% = 38.5 gallons.
Now we add the sump water volume to that and arrive at: 38.5
gallons + 10 gallons = 48.5 gallons. This is equivalent to
184.3l, or approximately 185 liters (1 gallon = 3.8 liters).
Liters are easier to use in our calculations.
Our calcium test reads 360 ppm. We want
400ppm. This means we must increase our concentration by 40ppm.
This is equivalent to 40mg/l or a one millimolar increase of the
calcium concentration. Remember calcium weighs 40g per mole.
Our solution contains 375g of CaCl2
per 5000 ml. This equals 75g per 1000ml (1 liter). One mole of
CaCl2 (anhydrous) weighs approximately 111g (110.986g
to be exact). How many moles do we have per liter of our
solution? 75g / 111g x 1 mole = 0.68 moles. Since there are 0.68
moles per liter, there are 680 millimoles (mM) per 1000ml or
0.68mM per ml.
We need a 1 millimolar (millimoles per
liter) increase in Ca concentration. Our tank holds 185 liters of
water, so we need 185 millimoles of Ca. Our solution contains
0.68mM of calcium per ml. We then need 185mM / 0.68mM x 1ml =
272ml of our solution. Equal amounts of all solutions are then
added to the aquarium.
Note: When making such a large
adjustment it is better to go slowly. This is what happens by
following the 30ml daily routine. After the concentrations are
where they should be, such large adjustments should no longer be
necessary. 30ml once or twice a week, per 100 liters
(approximately 25 gallons) of aquarium water should be ample as a
maintenance dosage.
A similar example can be found on this web sight (Calculating how much Calcium to add,
by Marty Boeckman)
This may seem complicated at first. After several computations
it will become much easier. Remember though that we estimated
several factors and rounded others. Again,
I cannot stress enough, the importance of diligently testing the
water conditions and observing the animals' reactions.
Note: Available calcium is also largely dependent on the
amount of magnesium in the system. In other words, if the amount
of available magnesium is depleted by say pink calcifying algaes,
then the amount of available calcium will drop, due to the
development of calcite. There is an extremely informative article
on this on this web sight (Kalkwasser,
Carbonate and Clumping, by Richard Greenfield).
Strontium: Sr; Sr2- (ion); 87.62 (weight); 7-8 ppm (desired concentration)
Strontium is a necessary element for various corals (hard
and leather corals). It performs vital functions in the uptake
and use of calcium by these corals.
Care must be taken when dosing strontium. Erratic and too
high doses of strontium (and also calcium for that matter) can
lead to cramping of some smooth mushrooms (actinodiscus; smooth
discosoma). In other words, regular dosing of smaller amounts is
to be desired. It is also reported that strontium is only
detectable for 36 hours after dosing. I have not tested this
myself, but then I test my water several hours after dosing
anyway.
(According to Ernst Pawlowsky and
Jürgen Thurau)
100g of SrCl2
(strontium chloride) are dissolved in 1000ml of water.
Dosage:
Initially, 0.5ml of this 10% solution (weight / volume %) is used
per 150 liters (approximately 40 gallons) of aquarium water, per
week. Slowly increase the dosage to 1ml per 150 liters per week.
This is the maximum recommended dosage.
A 10% SrCl2 solution is
equivalent to a 0.63 molar (moles per liter) solution.
1 mole of SrCl2 = 158.526g
Iodine: I (or J); I-
(ion); 126.9045 (weight); 0.02-0.04 ppm (desired concentration)
Iodine is needed by various algaes, fish and shellfish.
Iodine is also an important substance for the growth of
mushrooms. Too much can lead to overgrowth of various algaes
(especially bubble algae).
(According to Fossa/Nilsen, modified by Jürgen Thurau)
100g of KI (potassium iodide) are dissolved in 1000ml of water (stock solution). This is a 10% (weight / weight %) solution.
10ml of the stock solution are added
to 990ml of water to make a 10% additive solution. This is an
example of a volume / volume percentage.
Dosage:
2.5ml per 100 liters (approximately 25 gallons) of aquarium
water, per week.
The 10% stock solution is equivalent to a 0.60 molar solution.
The additive solution, which is 10% of the stock solution,
is 0.06 molar.
1 mole of KI = 166.0065g
Trace element solutions can be made for most any element. For the minute amounts of most other elements needed, commercial additives are the better solution.
Magnesium could easily be adjusted by making a magnesium chloride (MgCl2) solution. I do not have any data on such a solution at this. I also have not made this solution yet myself. I am planning on it in the near future though.
Nitrate can be added (?!?!?!) if necessary. Nitrates are needed by some brain corals and clams. By dissolving 1g of sodium nitrate (NaNO3) in 1000ml of water, a stock solution is prepared. At most 10ml of this solution are added per 100 liters (approximately 25 gallons) per week. Carefully watch this parameter if artificially adding nitrate please.
If any other commercial additives (e.g., Vital Gold or
Combisan) are added, take the additional calcium, strontium and
iodine into consideration. Homemade solutions may not be needed.
At the very least less of the individual solutions will be
necessary.
Meernachrichten Marinlife, April 1997 (#25), Jürgen Thurau
Das Aquarium, # 315 & 317, Dieter Brockman and Alf Nielsen, Hans Werner Balling
Das Aquarium, # 301, Ernst Pawlowsky
Korallenriffaquarium, Band 1, Fossa/Nilsen
Riesenmuscheln, Daniel Knop
Albert Thiel's Web Sight, Albert Thiel, et al
The Marine Aquarium Handbook, Martin Moe
In the third and final installment, I will list some of the most common measures, conversions and some other useful data.
Part I: Inorganic Substances as Additives in the Marine Aquarium
Part III: of Inorganic Substances as Additives in the Marine Aquarium