Activated Carbon
Many of us are familiar with the use of charcoal in the old cornerbox 
filters of our freshwater days. These usually consisted of small, 
shiny, irregularly shaped pieces of bone or wood charcoal. This type 
of carbon is not really suitable for use in marine aquariums and has 
been replaced by "activated" carbon. In this form the carbon has been 
subjected to extremely high pressures and temperatures to drive out 
all impurities and gases leaving behind extremely porous and pure 
grains of carbon. Particle size, type of gas used, activation 
temperature and, in some instances, inorganic salts of zinc, copper, 
phosphate, silicate and sulfate added before activation, provide 
carbon with specific adsorption characteristics (Moe, 1989). 
Therefore, activated carbon can be tailored to the specific type of 
impurities that one wishes to remove. By creating such extremely 
porous structures within the carbon grains we have, in effect, created 
a gigantic sponge that can absorb many impurities from the passing 
water.

In order for this absorbtion to take place, water must flow through 
the carbon. Although simply placing the carbon in the sump beneath the 
aquarium may suffice, the most efficient use of the carbon will occur 
if water is actually forced to go through it. This can be achieved by 
placing the carbon beneath the outlet of the overflow or by using it 
in a separate canister filter.

One of the most common questions concerning the use of activated 
carbon is how much to use and how often it should be replaced. These 
questions are very difficult to quantify simply because no two systems 
are identical. Differences in bioload and the type of organisms being 
kept greatly influence the type and amount of DOC produced. For 
example, aquariums filled with macroalgae will produce a greater 
variety of DOCs than systems with very little algal growth. Wilkens 
and Birkholz (1986) recommend 500 grams per 100 litres. Although this 
does seem excessive one could use this as an upper figure and work 
downwards. The real indicator will be the condition of the inhabitants 
in the system and the colour of the water. Too many aquarists today 
are turning towards technological wizardry to maintain their 
aquariums. People are constantly talking about ozone, redox potential 
and carbon dioxide systems when the majority cannot correctly identify 
their tank inhabitants or don't fully understand what alkalinity is. 
The occupants of our aquariums are far more sensitive to water 
chemistry than any instrument and if one spends more time watching 
them instead of the flashing lights on your equipment, you will be 
more in-tune with what is really going on in your tank.

For the same reasons mentioned above, it is difficult to recommend a 
specific time period after which the activated carbon should be 
replaced. However, various authors have stated that activated carbon 
should remain active for 5-7 months before needing replacement (Moe, 
1989; Wilkens and Birkholz, 1986). Usually, the presence of yellowing 
substances in the water can be used as a guide to determining if your 
activated carbon needs replacing since these are easily removed by 
activated carbon and will start to accumulate when the carbon begins 
to lose its activity. Moe (1989) describes the following method. 
Obtain a strip of white plastic and colour one half a faint yellow 
with a marker. Place the strip in the water and observe from a 
distance. When you can no longer distinguish the yellow half from the 
white half, your water contains yellowing substances and you should 
replace your activated carbon.

There are numerous brands of activated carbon being marketed today, 
some of which have fancy names such as research grade. Unfortunately, 
not all activated carbon is created equal and the levels of efficiency 
and quality vary greatly. The grains of activated carbon should be 
small, dull black in colour and as dustless as possible. Recent 
measurements of activated carbon filtered aquarium water have shown 
that certain brands will actually add phosphate to the water, which is 
exactly what we are trying to avoid. Some activated carbons contain 
high levels of ash that also can contribute to undesirable algae 
growth. If you are unsure if your carbon brand leaches out phosphate 
you can rinse the activated carbon in pure freshwater thoroughly and 
then use it. This should remove some, but not all of the phosphate. 
One way to determine phosphate release by carbon is to purchase a 
phosphate test kit. Perform the test on purified freshwater and then 
add a few grains of your activated carbon to the test vial. If you see 
blue trails behind the falling pieces, you will know that it releases 
phosphate. 

A final caveat concerning activated carbon is that it uncontrollably 
removes substances from the water, including some useful ones. 
Therefore, regular water changes or trace element additions 
(especially iodide) take on added importance when this form of 
chemical filtration is used for long periods or in large quantities. 
For example, when it comes to keeping delicate stony reef-building 
corals such as Acroporidae and Pocilloporidae, or soft corals such as 
Xenia, continuous use of activated carbon has been found to be 
detrimental for the reasons mentioned above (A. Nilsen, personal 
communication; D. Stüber, personal communication). Under intense 
illumination and continuous use of large quantities of activated 
carbon, coral bleaching and death are not unheard of. In some cases 
continuous use of activated carbon has led to reduced growth rates. 
For this reason many aquarists use activated carbon for only a few 
days each month, to quickly remove accumulated toxins from the 
aquarium. 

4) Lighting
Much has been written about the many forms and types of lighting 
available for use on reef aquaria. I do not want to discuss the pros 
and cons of all the various types as that could fill an entire book, 
suffice it to say, most will work fine provided you follow certain 
guidelines when purchasing them. First, the spectrum of light produced 
should not contain high amounts of red or yellow. Second, they should 
contain sufficient amounts of blue light. Third, they should not 
overheat the aquarium. Fourth, they must not emit ultraviolet light in 
large amounts (if they do, then the light fixture should have proper 
UV shielding). And fifth, they should provide adequate intensity for 
the depth and types of animals you will be keeping.

When dealing with fluorescent lamps, most meet the above criteria. 
However, beware of using so-called "plant lights" as they contain too 
much red in their spectrum and may promote the growth of undesirable 
microalgae. If you are using 8 or more lamps then you can use one such 
light to enhance colours if you wish, but they must not form the 
majority of the lighting. 

The use of metal halide lighting (specifically HQI, halogen quartz 
iodide) has increased greatly in the last few years. Again the same 
criteria mentioned above apply to these bulbs. To help ensure this, 
the colour temperature of the bulb should be over 5000 Kelvin and the 
colour rendition index (CRI) should be over 90. These values are 
usually printed in the literature or ad copy of the bulb. When used 
properly, these bulbs give excellent results but they tend to be more 
expensive than fluorescents. To learn more about the pros and cons of 
these lamps and the theory used to develop the above guidelines see 
Delbeek (1990c). 

As I mentioned earlier, this article is based on how I would setup a 
reef aquarium of 65 gallons. This type of aquarium could easily be lit 
by 6-8 48" 40 Watt fluorescent lamps and give excellent results with 
the majority of corals available. I generally recommend a 1:1 wattage 
ratio of blue and daylight spectrum lamps such as the Philips Actinic 
03 and the Sylvania Daylight, respectively. The choice in fluorescent 
lamps is seemingly endless and the types you choose will ultimately be 
determined by their availability. Of course you can also use high 
output fluorescents of say 60 W if you prefer and if you use specular 
aluminum reflectors you will get even more usable intensity. For tanks 
of greater height, light intensity becomes more of a factor. Generally 
speaking, tanks 24" high or greater will require using high output or 
even very high output (VHO) fluorescent lamps or metal halide. These 
fluorescent lamps will require different ballasts than regular 40 W 
lamps, so you will need to take this into consideration when choosing 
or changing the lighting system.

The lighting should be set on timers so that you can ensure the proper 
photoperiod is maintained. Generally, 10 hours of fluorescent lighting 
is adequate and 4-8 hours of metal halide, supplemented with blue 
fluorescents, is sufficient. You could also use additional 
fluorescents to supply light before and after the metal halides come 
on. You can also set the timers so that the lights come on and go off 
in sequence, simulating changes in light intensity over the day.

5) Water Quality
Of course irrespective of the filtration and lighting systems, if the 
proper water quality cannot be maintained, the animals will not 
survive. Water quality is a rather amorphous term and encompasses 
many different things some of which we can easily measure and some we 
cannot. Water chemistry is one portion of water quality that must be 
maintained within certain limits. Generally speaking the following 
parameters are of concern: specific gravity, temperature, pH, 
alkalinity, calcium, ammonia, nitrate and phosphate.

a) Specific Gravity
Specific gravity is used to measure the relative salinity of seawater 
compared to distilled water. Distilled water has a specific gravity of 
1.000 while seawater ranges from 1.022 to 1.030 depending on the 
region. The specific gravity is measured with the use of an hydrometer 
and should be between maintained between 1.022 and 1.025.

b) Temperature
As was mentioned previously, maintaining a proper temperature is 
critical for reef aquariums. If you cannot provide the correct 
temperature range you will not be successful no matter what else you 
do. The temperature should be between 74 and 78oF for the best 
results. If the temperature varies a few degrees during the course of 
the day this is usually not a problem. The most common problem is too 
high a temperature, that is 80oF+. There are a number of possible 
solutions to this and one or all of them may be necessary. First you 
should ensure that the top of the tank has adequate air circulation, 
either by having a hanging light fixture over the aquarium or by 
having a well-ventilated light hood. This will aid gas exchange and 
evaporative cooling, and will retard heat build-up in the hood. You 
could also design your sump so that it is open and provides a large 
surface area for evaporative cooling. Evaporative cooling can be 
further enhanced by placing a fan over the water surface. The most 
expensive but effective solution is to purchase an aquarium chiller 
designed for saltwater use. Somewhat less expensive is to purchase an 
air conditioner unit for the aquarium room. This has an added benefit 
for the aquarist of course, which may help you convince your spouse of 
the extra expense!

c) pH
The pH of aquarium water is a measure of the concentration of hydrogen 
and hydroxide ions. If the hydroxide ion is in greater abundance in a 
solution then the solution is said to be basic. If the hydrogen ion is 
more common the solution is acidic. Values of pH range from 0 to 14. 
If the number is less than 7 the solution is acidic, if it is greater 
than 7 it is basic and if it equals 7 it is neutral. Seawater is a 
basic solution with a pH of 8.2 to 8.4. In our aquariums, natural 
processes tend to lower the pH and we need to keep an eye on it. The 
pH is easy to measure with a saltwater pH test kit and should be 
maintained between 8.0 and 8.5. A sure sign that the pH is too low or 
high is the failure of your corals and clams to open completely.

d) Alkalinity
This is a term that has caused a great deal of confusion amongst both 
novice and advanced hobbyists. Stated simply the alkalinity of a 
solution is its ability to act as a pH buffer against drops in pH. The 
greater the alkalinity the greater its ability to prevent rapid pH 
swings. Once the alkalinity is exhausted the pH can fall rapidly. 
Alkalinity is provided in the aquarium by various negatively charged 
ionic compounds (anions) such as carbonates, bicarbonates, borates and 
hydroxides, to name just a few. The rather confusing term carbonate 
hardness has also been used to describe alkalinity, but this refers 
only to the carbonate and bicarbonate portions of alkalinity and does 
not take into consideration the other compounds involved. Therefore 
alkalinity is generally slightly higher than carbonate hardness 
(Spotte, 1979). 

To further add to the confusion, there are two different units of 
measurement used. There are numerous test kits available and they are 
all simple to use. Some test kits for alkalinity use the metric unit 
of milliequivalents per litre (meq/L), while other kits use the German 
unit, degrees of carbonate (German = karbonat) hardness (dKH). To 
convert meq/L to dKH simply multiply by 2.8. Natural seawater has an 
alkalinity of 2.1 to 2.5 (6-7 dKH). Alkalinity values in the aquarium 
should be maintained between 2.5 and 3.5 meq/L (7-10 dKH) through the 
use of commercial buffers. These buffers should also be used to 
maintain pH. There a numerous powdered buffers available that will 
maintain both alkalinity and pH, and the majority work very well by 
raising the alkalinity without causing rapid changes in pH. Beware of 
any buffers that cause rapid changes in pH.

e) Calcium
Calcium is the primary building block of the corals, clams, calcareous 
algae and many other organisms that we would like to grow in our 
aquariums. Without adequate supplies of calcium these organisms will 
not flourish and most will eventually waste away and die. Calcium 
levels are measured in parts per million (ppm) or milligrams per litre 
(mg/L). Calcium levels in natural seawater range from 380 to 480 mg/L
depending in location. In our aquariums calcium levels should be 
maintained between 380 and 450 mg/L to ensure proper growth and 
longevity of our animals. 

How one obtains these levels is a matter of choice and debate. Some 
advocate the use of powdered calcium chloride while others recommend 
powdered calcium hydroxide. There are also numerous calcium 
supplements on the market with wonderous claims as to their 
efficiency. It remains to be seen how well these products will perform 
over long term use. 

Calcium chloride is easy to use and does not directly affect the pH of 
the aquarium. The danger in its use is that one can easily overdose 
and quickly raise the calcium ion level in the aquarium. This has two 
effects. It raises the specific gravity rapidly and it can cause a 
rapid drop in alkalinity, and subsequently, pH. Calcium chloride can 
be added directly to the sump as a powder but it is best to dissolve 
it first in freshwater and slowly drip it into the aquarium.

Calcium hydroxide is messy to use, has a high pH that can be hazardous 
as it can rapidly raise the pH if it is added too quickly, and it is 
caustic. It does add calcium slowly to the aquarium and does not 
deplete alkalinity. Generally sold as a powder, it is added to 
freshwater at the rate of 1 teaspoon per gallon (1.5 grams per litre). 
This solution, commonly called kalkwasser (German for calcium water) 
is then shaken and allowed to settle. The clear liquid that results is 
then slowly added to the aquarium as make-up water for evaporation. 
This is best done using a float valve or dosing pump. For more details 
on calcium additions see Sprung and Delbeek (1990) and Sprung (1991).

Calcium ion concentration can be easily measured using available 
calcium hardness test kits from chemical supply companies such as Hach 
and LaMotte, or your local pet store.

One last note concerning calcium. If you have access to freshwater 
that is low in organics, nitrates and phosphates, and is high in 
minerals such as calcium and magnesium, then you may not require the 
use of calcium supplements if you use this water for evaporation 
replacement.

f) Ammonia and Nitrate
Normally, ammonia levels in the aquarium should be zero. If you can 
measure detectable ammonia, your aquarium has either not yet cycled 
completely or you something is decaying in the aquarium. If the former 
is true, you should wait until the level drops or if you have animals 
that are suffering you can use one of the commercially available 
ammonia neutralizers. In the case of the latter, you should carefully 
and completely inspect your aquarium for any decaying animals, food or 
live rock, and remove it immediately. Organically decaying live rock 
is easily recognized by the smell and the white slime that usually 
accompanies it.

Nitrate has often been implicated as a causative agent for failure in 
reef aquariums. However, if the truth be known, there has never been 
any conclusive evidence for this. As mentioned above, nitrate levels 
of 40 ppm have been measured in aquaria with large stony coral growths. 
It would safe to say that maintaining a low level of nitrate 
is still desirable, but one need not become fanatical about it. Where 
nitrate could still pose a problem though, is in undesirable algae 
growth.

g) Phosphates
Phosphates can cause problems in marine aquaria, especially reef 
aquaria if they are allowed to build to levels above 0.2 ppm. 
Elevated phosphate levels will fuel unwanted algae growth and 
interfere with the calcification processes of corals and coralline 
algae. Phosphates are present in many forms in the aquarium, not all 
of which can be easily measured. The real trick with maintaining low 
phosphate levels is to minimize their input and maximize their 
removal. 

Minimizing input relates directly to the quality of the freshwater you 
are using for evaporative top-offs. This water should be as free of 
phosphate and nitrate as possible. If you are using this water to make 
kalkwasser then the high pH of this solution will result in the rapid 
precipitation of any remaining phosphate, in the form of calcium 
phosphate. Beware also of any additives and salt mixes that may 
contain unacceptable levels of phosphate. Avoid using any liquid food 
supplements that may contain phosphate and check your activated carbon 
to make sure it does not release phosphates. 

Although some have advocated minimal feedings of the fish 
in a reef tank, this is not always a wise practice. Unless adequate 
food is available, the fish will slowly waste away. Careful, moderate, 
but frequent feedings of high quality foods, should be carried out 
several times a week, if not daily. Some more active fish such as 
Pseudanthias spp. require small feedings several times a day to 
maintain their health. Tangs and surgeon fish do not usually get 
enough vegetable matter to eat in a reef tank and these fish should be 
provided with a constant supply of vegetables such as leaf lettuce, 
bok choy, zucchini or seaweeds used for sushi such as nori.

To maximize the output of phosphate the use of adequate protein 
skimming is essential. Also the frequent (every 2-3 days) cleaning or 
replacing of the prefilter is a must. In aquariums with poor water 
flow, the regular removal of detritus from beneath and between the 
rocks should be a part of your monthly routine.

6) Trace Elements
The topic of trace elements has become quite popular again in the last 
few years. As a rule, very little is known about what elements corals 
require to grow and survive. At this point it is safe to say that 
strontium is a very important element in the growth of many calcareous 
organisms. Strontium supplements can now be purchased in almost any 
marine reef aquarium store. Iodide appears to be another important 
trace element for corals, clams and crustaceans. Again, potassium 
iodide and other iodide sources are readily available for purchase. At 
the time of this writing, there is no substantial evidence for the 
importance of any other elements. That is not to say that in the future the
 importance of others will not come to light, but for now, these two are the
 only ones I can definitely say in my experience, are necessary for optimum
 growth.

7) Aquarium Design and Set-up
Although there are many ways to set-up a reef aquarium, I tend to 
favour a very simplistic approach. You may wish to follow my example 
or make the modifications I will include as options.

At this point I assume that you have already choosen the size, shape 
and location of your aquarium. Also you have decided upon, and 
installed, the type of overflow and lighting system you will be using. 
Now comes the next major decision. Do you go with protein skimmers 
only or will you be using a trickle filter in combination with a 
skimmer? Most aquarists feel more comfortable with the latter. Using a 
trickle filter gives you several options later on. First of all, once 
the tank is up and running well, you have the option of removing the 
biological media if you so desire. Secondly, the trickle filter gives 
you a ready made (albeit expensive) sump that you can use for 
activated carbon, float valves and any other additions you might like 
to make. 

If you will be using a trickle filter it is best to cycle the filter 
separately. This is best done by directing the output of the filter 
directly back into the overflow, by-passing the tank. This will allow 
you to prepare the bacterial bed in the filter without having to fill 
the main tank. One then adds one of the commercially available 
ammonium chloride solutions to the filter and a bacterial culture, 
either bottled or through the addition of a cupful of gravel from an 
established aquarium. Once you can no longer measure any ammonia, the 
filter will be ready. This will usually take about 4 weeks. Empty the 
filter of all water and refill with new seawater. This removes any 
nitrate and nitrite that may have accumulated. Also at this time you 
can check for any leaky valves or fittings and reseal them. While you 
are waiting for the filter to cycle you can order your live rock and 
fill the aquarium with pure freshwater, either distilled, reverse 
osmosis or deionized. Then add the salt mix and a few powerheads to 
circulate everything.

I prefer making a simple sump without a trickle filter, out of a 15 or 
20 gallon aquarium from which I can pump water to my skimmer and back 
to the tank. You can then modify this sump tank any way you like. If 
you can plumb the water flow coming from the aquarium so that it 
passes into the skimmer first, this will give you the most efficient 
design, however, it makes it diffuclt to control the flow rate through 
the skimmer. Otherwise, simply let the water flow into the sump and 
then pump it back to the aquarium. If your skimmer is tall enough, you 
can pump the water into the skimmer and then let it flow directly back 
into the tank from the skimmer. Or you can pump some water from the 
sump into the skimmer and return the rest directly to the aquarium. 
The water from the skimmer would then simply return to the sump to be 
recycled. I prefer to use two water pumps. One to pump the water from 
the sump to the skimmer and then back to the sump, and one to pump 
water from the sump directly to the aquarium. This way I can easily 
adjust the flow of water through the skimmer without affecting the 
water flow to the aquarium and visa versa.

Just a brief word about the types of valves included with most 
commercial skimmers. To control water flow most people use ball 
valves. These valves are great as a on-off control of water flow but 
are very difficult to use for fine adjustments in flow rate. The best 
valves to use for this are gate valves. While more expensive, they are 
infinitely better than ball valves when it comes to making fine 
adjustments in water flow, and I strongly urge that you use them on 
your skimmer inlet. You will save yourself a lot of headaches. 

Some have argued that they do not want a 2' or 4' skimmer sitting in 
their living room. There are several ways around this problem, limited 
only by your ingenuity. If the stand was designed tall enough, you 
should be able to easily place two 2' skimmers underneath it. You can 
also design the stand and canopy so that one end of the tank is 
enclosed and a 4' skimmer rises within the enclosure. Other options 
include using screens, building the filtration system into an adjacent 
closet or wardrobe cupboard, or even placing it in another room or 
basement and running water lines through holes in the wall or floor to 
the tank. I have seen all of these options and they work very nicely. 
There is no need to have unsightly filtration equipment out in the 
open, all it takes is some imagination.

Once your aquarium is completely set-up and running you can add the 
live rock and whatever material you have chosen for the bottom. Most 
reef aquarists choose not to use any bottom substrate. This makes it 
much easier to keep the aquarium clean and allow adequate water flow 
around the rocks. Once your soft corals and coralline algae begin to 
grow, you will not see much of the bottom anyway. It is possible to 
have a substrate but it is much easier to run a reef tank without one. 

The live rock should be prepared and arranged as described above and 
then added to the aquarium. Once the rock has been introduced keep the 
lights off for at least two weeks. This will retard the immediate 
growth of any microalgae as a consequence of excess nutrients being 
produced by any die-off of organisms such as sponges on and in the 
rock. Continue to monitor ammonia levels during this period. If 
ammonia levels become undetectable at the end of these two weeks then 
you can proceed on to the next step. If ammonia levels remain high 
then you must wait until they drop. Although there all kinds of 
elixirs that can be used to neutralize ammonia, I prefer to let nature 
take its course, what's the rush? During this period you should also 
check your pH, specific gravity, alkalinity and calcium levels and 
make adjustments as required.

Once the tank has cycled and the rock looks clean and fresh i.e. no 
white slime on it, then you can turn on the lights and start adding 
organisms. The key during the whole start-up process though is 
PATIENCE! Don't rush at this point and add all sorts of specimens or 
else you will be disappointed later!

The first things to add should be your "maintenance crew" that is the 
scavengers: algae and detritus eaters. These organisms are especially 
important if you use a substrate, i.e. they will help to keep it clean 
and turned over. Under this category are brittle seastars and detrital 
feeding sea cucumbers (not Sea Apples!) that can be easily recognized 
as they have oral tentacles designed for sweeping over the rocks and 
substrate as they crawl over the substrate. Herbivorous snails should 
also be among the first additions. Species such as Astrea tecta
are especially desirable. Larger snail species tend to bulldoze their 
way over rocks and corals, often displacing pieces. Start off with as 
many as one snail per 2-4 gallons of water. I would also recommend 
that at this point you add your first fish which should be one of the 
tang species, preferably the Yellow Tang (Zebrasoma flavescens) 
and/ or the Kole Tang, Ctenochaetus striatus, to help control 
the growth of undesirable algae.

You may have noticed that I have not recommended adding any sea
urchins. There are a couple of reasons for this. First of all urchins
tend to be bulldozers and can tear down a reef tank faster than you
can set it up again! Furthermore, some species of urchins actually
grind away at rock and burrow into it during the day. This tends to
diminish your live rock supply and creates quite a bit of detritus in
the process. Many species will attempt to camouflage themselves with
whatever is lying around the tank, including your, previously, well-
attached soft corals. Finally, urchins tend to scrape live rock right
down to the limestone, which means they will remove all those nice
coralline algae you paid for and have been lovingly cultivating for
months.