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Alkalinity, what does it mean?
Alkalinity, or more commonly
referred to as, carbonate hardness is a term that is often
thrown around, but what does it mean?
We know we need to test for it.
We know corals need it to grow. But what is it, and why is
it important?
For the purpose of this brochure
we will define alkalinity as this:
Alkalinity
is a measure of the acid neutralizing capacity of water.
Acid neutralizing capacity means the ability to accept acid
without a subsequent drop in pH. Alkalinity is basically a
measure of how much antacid is dissolved in the water. The
more acid that can be added to water before the pH starts to
drop, the higher the alkalinity. |
Talk to our
sales team today about test kits and additives to assist you
with maintaining your aquarium’s alkalinity.
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Reefers measure alkalinity with a test kit. How does that
work?
Well, in effect test kits
do a pH endpoint titration. They all include pH indicating
dyes (providing a color change) and an acid (frequently
dilute sulfuric acid) to lower the pH. You typically add
acid until the dyes turn color. Since these dyes are
selected to have a color change in the pH = 4 to 5 range,
what you get is a measurement of how much acid it takes to
lower the pH to that range. This color change is used to
approximate the endpoint of the titration, giving you the
total alkalinity (or “TA”).
Why is alkalinity important to my tank
and corals?
Corals and other
organisms deposit calcium carbonate in their skeletons and
other body parts. In order to do this they must generate
calcium and carbonate at the surface of the growing calcium
carbonate crystal. While it would take pages to describe
this process, it is readily apparent that if corals deposit
these chemicals, they are using them up from the water that
they inhabit. So, if that’s the case, why not just measure
carbonate as we do calcium?
Well, there are two answers. The first is that there is no
simply way to measure carbonate with a kit without doing a
pH titration as an alkalinity test kit does. Second, corals
may actually use bicarbonate instead of carbonate as their
ultimate source of carbonate. If we could easily measure
bicarbonate, we’d probably be doing just that.
So what we are doing is using a very simple alkalinity test
as a surrogate measure for bicarbonate and carbonate. Since
these two substances comprise the great majority of
alkalinity in seawater, it is safe for most people to say
alkalinity is the
"availability of bicarbonate and carbonate
for my corals".
We recommend maintaining an
alkalinity of 8-12dkh, to keep a stable alkalinity in your
reef aquarium!
Common indicators of Alkalinity problems!
As your aquarium begins to grow,
and you begin to add more coral, you will soon discover the
amount of carbonates required to maintain stability, and
growth, will increase.
How do I know my demand for carbonates has increased?
They are a couple of
common indicators.
Often, low alkalinity can be
associated with low ph. If ph is consistently low, a simple
test for carbonate will usually indicate a deficiency in
alkalinity. Using an additive or buffer to raise the waters
carbonate hardness often remedies both problems.
Slow coral or coralline growth
is a less obvious indicator that carbonates may be
deficient. Again, testing a sample of your aquariums water
and making the appropriate adjustments with an adequate
buffer may be a remedy. |
