Description
This article is from the Beginning
Saltwater FAQ, by Thomas Sasala with numerous contributions by
others.
02 The Basic Parameters
So what's different about saltwater versus freshwater? As alluded to
above, saltwater fish are more sensitive to changes in their
environment. The critical parameters of a saltwater tank are pH,
nitrate, salinity, and temperature. During the cycling process,
ammonia and nitrite can also be a problem. These elements are not
different from those of a freshwater tank, but the degree to which
they may stray is vastly different.
The pH of a marine tank is one of the most important parameters.
Marine fish and invertebrates are especially sensitive to rapid
changes in their pH, so keeping pH fluctuations within 0.2 each day is
very critical. All marine creatures like a pH near 8.2, ranging from
8.0 to 8.4. The pH should never drop below 8.0.
The next critical parameter is nitrates. Saltwater fish are more
tolerant of higher nitrates than invertebrates (in general), but still
like nitrates lower than 20ppm, with less than 5ppm being required for
most invertebrates. Reef keepers tend to quote anything higher than
0.5ppm as unacceptable, but this is an unrealistic goal for fish-only
or minimal invertebrate tanks.
The next parameter of concern is salinity, or specific gravity.
Loosely (very loosely), specific gravity is the amount of salt in the
water. Many aquarists treat specific gravity and salinity as one and
the same, but technically speaking, they are not. Specific gravity is
temperature dependent and salinity is not. Most hydrometers
(hydrometers measure specific gravity) are calibrated to read the
correct specific gravity at 59F. Since this is a little low for most
tanks, hobbyist grade hydrometers are usually temperature corrected to
read the correct specific gravity at or around 77F (25C).
In any case, most creatures will acclimate to almost any specific
gravity (within reason), so long as it does not vary widely. The
specific gravity of a saltwater tank should be around 1.022. It's
worth noting that the salinity of natural sea water varies according
to location (ocean, to lagoons, to estuaries), ranging anywhere from
1.020 to 1.030. So different fish might be native to different
salinities, and may need some time to acclimate to a different
salinity.
Finally, the temperature of a saltwater tank is basically the same as
a freshwater tank. Anywhere between 75F to 80F (24C - 27C), with 77F
(25C) being a good midpoint. Wild temperature variations increase fish
stress and invariably lead to disease, so a good heater (or chiller)
is a must. As an aside, submersible heaters tend to be preferred over
hang on the back kinds. Also, they seem to be somewhat more reliable
than the less expensive `clip-on' kind.
Other parameters worth keeping an eye on are alkalinity and calcium.
The alkalinity of a saltwater tank is really critical for long term
success. Without a decent alkalinity reading, the pH of the tank will
drop over time and endanger the lives of your pets. The alkalinity of
a saltwater tank should be around 2.5 to 3.5 meq/l.
Calcium is more of a reef keeper's issue than a fish-only tank.
However, once you advance and wish to keep invertebrates, monitoring
calcium levels becomes a must. Without calcium, and other trace
elements, invertebrates can not properly form their exoskeletons and
will not survive. Calcium levels should be 400 to 450 ppm Ca++. For
more information about adding calcium, see the REEFKEEPERS' FAQ.
Some of the more easier to keep invertebrates, such as shrimps, also
need regular supplements of iodine and other trace elements. Most
foods will supply the necessary amounts of these elements. However, if
you are using a protein skimmer, these elements will be stripped from
the water and need to be replaced manually. Once a gain the
reefkeeper's FAQ has more information about trace element additions.
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aquaria, fish, acquarium, tank, fishkeeping, saltwater
