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
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
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++.
Now that we are comfortable with the basic parameters of a
saltwater aquarium, let's look into what is needed to run a
The components needed to run a successful saltwater tank depends
a lot on who you talk to. You should never operate solely
under the advice of one person. For example, many people advocate
using under gravel filters for biological filtration. This however,
must be tempered with wisdom. A saltwater tank running an under
gravel filter (UGF) with minimal circulation will be much more work
than a than a system running a wet/dry filter and a couple of
powerheads. Wet/Dry filters tend to require less maintenance, as
UGF's tend to become clogged over time.
Not to get too buried in details, the basic components of a
saltwater tank are the tank, decorations, filtration (including
protein skimming), lighting, water, and test kits.
One of the most important decisions in starting a saltwater
aquarium will be the size of the tank. The basic rule of thumb is
the bigger the better. A larger tank will be easier to control and
gives a bit more leeway for mistakes (which are inevitable). The
smallest tank for beginners should be no less than 20 gallons, with
55 gallons being even better. For someone versed in fish keeping
(i.e., converting from fresh to saltwater), a 10 or 15 gallon tank
will work, but is not suggested. In general, fish like long, wide
tanks. The more surface area a tank has, the better the gas exchange
will be and the happier the fish will be.
Before finalizing on a tank size, remember that fish densities
are much lower for saltwater than freshwater. That is, you can not
put as many fish in a saltwater tank as you can in a freshwater
tank. Putting more than 2 saltwater fish in 10 gallon tank is asking
for trouble. A general rule of thumb is 4" (10cm) of small-to-medium
fish per 10 gallons, or 2" (5cm) of larger/fast growing fish per 10
gallons. This is just a rough estimate of the number of
fish. There is no exact number since finding the stocking density
has to take into account the filtration, maintenance, feeding
Beyond the number of fish you wish to keep, the tank's size will
also affect your filtration and lighting choices, both in cost and
design. Tanks which are 48 inches (122cm) long are usually cheaper
to light because the lamps are more readily available. However, the
larger the tank, the more light you will need to provide your
inhabitants. Moreover, a larger tank needs efficient filtration to
keep the system thriving. A good size tank is around 55 gallons.
As a note, scrutinize hoods carefully. Many of them are designed
for 48" tanks, but require two 24" lamps rather than one 48" lamp.
(24" lamps are usually more expensive than 48" lamps.)
Once you have decided on a tank, make sure you have a place to
put it. The tank should not be in direct sunlight or in an area
which is very drafty. Also, make very certain the stand will be
capable of holding the weight of the tank, plus substrate, plus
rocks, plus water. In total, a 55 gallon tank will probably weigh
over 800 pounds.
After selecting the tank, consideration must be given to the
substrate. It is best to use a calcareous substrate such as crushed
coral or dolomite. These substrates will, at least initially, help
buffer the water by adding ions to the buffering system. Generally
the substrate should not be so tiny as to get sucked into the filter
or pumps, and not so large as to make the tank unsightly. Also, some
fish (e.g., Gobies) like smaller grades of substrate over larger
ones. Something in the 2-5mm department seems average.
Live sand is one substrate which has recently gained a fair
amount of publicity. This technology is really in its infancy and is
not recommended for beginners.
After you select a substrate, consider the filtration system you
plan to use. Your choice in filtration may impact the amount to
substrate you need. A UGF or RUGF filter should have about 2-3"
(5cm) of medium grade (2-3mm) substrate covering the filter plate.
You do not need substrate when you use non-UGF filters (e.g.,
hang-on-the-back power filters), but, most people use between a 1/2"
to 1" for such tanks. It's interesting to note that too much
substrate in a non-UGF system might lead to dead spots, which can
kill your inhabitants (a plug for regular gravel cleaning). More
detailed information about filtration can be found in the
Next, consider the decorations, of which there are a cornucopia
of choices. Dead coral, lava rock, tufa rock, live rock, and many
more. Coral pieces are the most popular, but are also some of the
most expensive. Lava and tufa rock are inexpensive and may also be
stacked to make interesting reef looking tanks. Live rock is one of
those buzz words that people like to throw around and one which gets
a lot of hype. Live rock is simply rock taken from a reef system
which has been populated by many different organisms.
Many aquarist dedicated to fish-only setups are beginning to
discover the benefits of having live rock in their system. Live rock
produces a more natural environment for the fish and also aids in
nitrification and denitrification. This implies that the live rock
is more that just a decoration, it is actually part of the
filtration system. Although it is difficult to use live rock as the
sole source of filtration in a fish-only setup, it certainly can be
used effectively to reduce nitrates. The use of live rock in
fish-only setups must be closely monitored though. If nutrient
levels in the aquarium are high, the live rock will be the first to
demonstrate this fact. Live rock in presence of high nutrient levels
will grow unhealthy amounts of hair algae, and in some cases,
cyanobacteria (slime algae). To avoid outbreaks of plague algaes, a
few simple rules must be followed.
First, you must start will high quality live rock; live rock
which is highly encrusted in coralline algae. Avoid live rock which
already has hair algae growing on it. Regular additions of calcium
may also be needed to keep the coralline algae thriving. Next, you
need to keep nitrate levels low (~10ppm) and ensure you have nearly
undetectable levels of phosphate (~0.02 ppm). Finally, feed
sparingly; decomposing food is one of the main avenues for
introducing phosphate/nitrate and contributing to alga e problems.
If you plan to add live rock to your system, remember live rock
contains living organisms, so they can be killed along with any
other organism in your tank. It's a good idea to wait until after
the tank is set up before buying live rock. There is no good place
to store live rock other than in a circulating tank. Trying to do
otherwise will be disastrous and costly. Also, if you are going to
put live rock into an established tank, the rock must be cured live
rock (for a more detailed discussion of cured live rock.
Filtration is covered in detail, with most of the information
being relatively generic and applicable to marine tanks. However,
there are certain caveats that should be noted. If you decide to use
a UGF, reverse flow setups are better. A RUGF will keep nitrates
lower by keeping the substrate cleaner and will aid water movement
In addition to good filtration, water movement is a must in
saltwater aquaria. Without circulation the system will be unstable
and usually tends to grow unhealthy amounts of algae and other
undesirables. The easiest way to achieve water movement is to have a
powerhead in the tank for circulation. One must be careful though, a
medium sized powerhead in a small tank will easily make a tornado-
like environment and cause problems for small or slow moving
One of the best possible filtration systems for a fish-only
marine tank is a wet/dry filter. Although commercial setups are
fairly expensive, a wet/dry filter can be made very inexpensively at
home with little effort, (as well as other fish related projects).
Many people advocate wet/dry filters for marine tanks stating
they are the only acceptable solution. This is simply not true. Any
one of the popular filtration systems may be used for a marine tank.
The key to success is providing adequate biological filtration
without trapping excess detritus. Trapping detritus produces
nitrates and inevitably leads to problem algae outbreaks. Which ever
filtration system you choose, be sure to rinse the mechanical
filtration media at least once a week. Ideally you should
rinse the media in old saltwater from the tank to minimize the
disruption of any nitrifying bacteria growing on the media.
A part of filtration which most recently has gained wide spread
acceptance is protein skimming, or foam fractionation. Protein
skimmers are a must for a decently stocked saltwater tank as they
strip dissolved organic particles from the water before they can be
converted to nitrates.
There are simply too many models and manufacturers to discuss all
of them, but the two basic designs are air-driven and venturi.
Air-driven protein skimmers use a wooden or glass airstone to
produce bubbles in a column of water. Venturi skimmers use a venturi
valve to inject bubbles into the water column. Both air-driven and
venturi have co-current and counter-current designs, with
counter-current protein skimmers being far superior to co-current
In deciding on a protein skimmer, there are some basic things to
consider. Air-driven skimmers use airstones which must be replaced
on a regular basis (usually every month or so). Additionally, they
usually require more maintenance than venturi skimmers to maintain
proper skimming. Venturi skimmers on the other hand require very
powerful pumps to achieve effective protein skimming. They are
usually more expensive than air-driven skimmers as well. Also, any
skimmer smaller than 24" should be avoided for heavily loaded tanks.
Whichever type of skimmer you buy, the final cost of the skimmer
must not overlook the need for an external water pump and
potentially an air pump. A $200 venturi protein skimmer usually
doesn't include a $150 high pressure pump; a fact that most people
seem to miss the first time around.
With the setup nearly complete, you need to consider your
near-term and far-term lighting requirements. If you plan on having
a fish-only tank forever, then you only need a single full spectrum
bulb. However, if you plan to advance in your hobby and keep more
sensitive animals such as anemones, you must carefully select your
lighting (and filtration as well). Anemones require very strong,
full spectrum lighting, supplemented with actinic blue. The
general rule of thumb is a minimum of 3-4 watts per gallon, with the
higher values for deeper tanks (greater than 18-24 inches). The
standard Perfecto hood will not provide enough light to
keep anemones alive (or other light-loving invertebrates for that
For a beginning aquarist, fluorescent lighting is probably the
best. Metal halide lighting is really for reef keeping and heavily
planted freshwater tanks. In any case, if you want or will need
something more than a single lamp, your choices are limited. The
best thing to do is to build your own hood with custom lighting, or
buy one through mail order. Fish store prices usually preclude
aquarists from getting proper lighting.
If you select a custom fluorescent hood, then you will have to
choose between normal output (NO), high output (HO) and very high
output (VHO). Most people with fish-only tanks stay with NO lamps.
Both HO and VHO lamps require special ballasts, are more expensive
than NO lamps, and need to be replaced more often (more $$).
One critical item in a saltwater tank that doesn't really fit
into any of the above topics is that which sets it apart - the
marine salt. There are many different brands of salt on the market,
all of them being basically the same. The only difference among them
is whether or not they have nitrates and phosphates. Both of these
are very bad for aquaria, so salts which have them must be avoided.
Good salts include Instant Ocean (IO), IO Reef Crystals, and
Coralife. As a note, standard rock salt can not be used as a
substitute for marine salt mixes. Rock salt does not contain the
important elements that marine creatures need to survive.
To measure the specific gravity of your saltwater you will need a
hydrometer. There are two basic types of hydrometers available to
hobbyist, the floating kind which usually measures temperature as
well, and the plastic kind with a floating arm. It's basically a
toss up as to which one to get, but the plastic kind has a larger
scale and is easier to read.
The final component needed to run a successful saltwater aquarium
is test kits. In order of importance, they are pH, nitrate,
phosphate, alkalinity, nitrite, ammonia and Calcium (for reef tanks,
the calcium test kit is more important than nitrite and ammonia). A
good pH test kit is critical, and an electronic pH monitor is even
better. Ammonia and nitrite tests are only needed occasionally after
cycling. A nitrate test kit is a good overall test for water quality
after the tank becomes established. You should perform a pH test
once a week and a nitrate test every two weeks. The other kits are
not necessary, but may be needed to solve particular problems or
after you advance to more delicate creatures.
The following section briefly explains what you need to do to
initially setup your tank.
The first thing you need to do is to place the stand in it's
final position. Make sure the stand is level in all direction. Next,
place a piece of Styrofoam or rubber on the top of stand where the
tank will sit. This eliminates small gaps between the stand and tank
reducing pressure points which might cause the tank to crack after
being filled. After the stand is positioned, place the tank on the
stand. Make sure the tank is level in all directions. Note, a tank
that is not level has a great chance of cracking after it is filled.
Where ever you place the tank now is most likely where it will
remain for its lifetime. You should never move a tank that has water
in it since this is a sure way to crack it.
Once the tank is placed, install the filtration. If it is an UGF,
then place the filter plate(s) on the bottom of the tank. If it is a
wet/dry, then connect the prefilter and all the hoses.
Prior to adding the substrate, rinse it with plain water until
the water runs clear, and then add it to the tank. On top of the
substrate arrange the decorations. Now the saltwater may be added.
The easiest way to add water to a tank is to place a plate on the
substrate and pour the water onto the plate.
When initially setting up your tank it is okay to fill the tank
with dechlorinated water and then add the salt mix. However,
subsequent water changes need to be premixed. Pre-mixing saltwater
is done for two reasons, it gives time for the salt to thoroughly
dissolve and also allows the water parameters to stabilize. Adding
10 gallons of freshwater and then an appropriate amount of salt to
an established tank is a big mistake (and an excellent way to kill
One note on making saltwater. The source water you use for mixing
is extremely important to the overall success and health of the
system. There is more to be said about this later, but for now,
realize that tap water probably won't be good enough for your tank.
When all the water is in place, start up the filter system and
check for any leaks (of both water and air). Let the tank sit for a
day or so to clarify (with the filtration running). Now you can add
How many fish you add for the cycling process depends on the size
of the tank and the cycling method you choose. You can cycle a tank
without any fish at all. In this case, you add ammonium chloride to
simulate fish waste and an initial source of nitrifying bacteria. It
is best to get a bacteria culture from an established saltwater
tank. This can be in the form of some substrate, old filter media,
or some macroalgae such as Caulerpa spp.. Live rocks are also
an excellent source of nitrifying bacteria.
If you choose to cycle your tank using fish, which is infinitely
more interesting than a tank full of circulating water, the number
of fish needed depends on the size of the tank. In any case, two
fish are preferable to one. If one fish dies, you will still have
one to finish the cycling. Of course the second fish may pass on
too. If all the fish die, then you have to remove all the
contaminants from the tank and introduce more organisms (read this
as start all over).
Cycling doesn't have to be limited to fish though. Crabs and
mollusks can also be used. However, since these organisms don't
produce much waste, it will take longer to cycle the tank.