Ozone is often used
by reef aquarists to "purify" their tank's water.
To most aquarists this means making the water visually clearer,
so they elect to start using ozone to improve clarity. Not
everyone notices such improvements, however, and some aquarists
have been disappointed. What sort of changes can be expected
upon initiating ozone?
This article is the third in a series that
discusses the details of ozone and its use in reef aquaria:
and the Reef Aquarium, Part 1: Chemistry and Biochemistry
and the Reef Aquarium, Part 2: Equipment and Safety
Ozone and the Reef Aquarium, Part 3: Changes in a Reef Aquarium
upon Initiating Ozone
article in this series detailed what ozone is and how
it reacts with seawater. It also related ozone's perceived
benefits to the actual chemical and biochemical changes that
it can cause. The second
article described the equipment and processes used to
safely and effectively apply ozone in reef aquaria. This third
article details the changes observed in my aquarium system
upon initiating ozone. Through pictures and measurements,
it is hoped that aquarists can attain an understanding of
ozone's likely benefits before spending the time and money
necessary to try it for themselves. While the results will
not translate directly to every reef aquarium, my husbandry
practices are not unusual and these results seem to reflect
those found by a wide range of aquarists who have used ozone
The sections are:
The following sections detail a variety
of visual and chemical changes that I noted in my aquarium
upon initiating ozone. In most cases, I compare before and
after measurements or photographs to show the effects. Most
of the "after" cases were two weeks after initiating
ozone, but some were recorded or continuously monitored for
up to two months.
In order to evaluate whether the effects obtained in my aquarium
will translate to other aquaria, it is important to understand
how my aquarium is maintained and how the ozone was used.
Ozone was supplied by a 100 mg/hr Aqua Medic corona discharge
ozone generator. In most cases, an Optima air pump sent the
air through a Red Sea air dryer (500 g model) and then into
the ozone generator. I also experimented with a Tetratec Deep
Water air pump, with little difference noticed. The air/ozone
mixture was then mixed with aquarium water in three different
ways: a Coralife
ozone reactor, my skimmer (ETS 800 Gemini), or a tubing
reactor of my own design. The effluent air and water were
passed over granular activated carbon (GAC) before being returned
to the room and the aquarium, respectively (except when using
the skimmer, where no GAC was employed).
My aquarium system consists of two main tanks (120 gallons
and 90 gallons) and a variety of sump and support systems,
including skimming, large macroalgae and sand-filled refugia.
The aquaria contain a variety of fish, live rock, sand and
invertebrates, including both hard and soft corals. In short,
they are typical "mixed" reef aquaria. Near the
end of this article is a section that details
the nature of my aquarium system so that aquarists can understand
whether their system deviates from mine in some important
When ozone is first added to reef
(oxidation reduction potential) rises. What exactly this means
on a molecular level is complicated and not well understood,
but it is the expected result of oxidizing the various redox
active chemical species in the water. Some aquarists see a
big rise in ORP - large enough that they need to control the
ozone generator so that the ORP does not rise too high (>450-500
mV). Others see a relatively small rise, and still have ORP
in the 300 mV range even after using the generally recommended
amount of ozone. Some even find that it remains in the upper
200 mV range. This variability is important for aquarists
to keep in mind, and they should not conclude that there is
a problem if the ORP remains fairly "low."
In the absence of ozone, my aquarium seems to have an ORP
that ranges in the mid- to upper 200 mV range. While I monitored
ORP carefully when initiating ozone to be sure not to overdo
the addition, such concern was unfounded. Even when adding
ozone at full production (100 mg/h as claimed by Aqua Medic;
equivalent to about 0.5 mg/h/gallon of display volume or 0.3
mg/h/gallon in the entire system), the ORP never rose above
about 335 mV. Even with newly dried desiccant in the air dryer,
a freshly cleaned skimmer and ozone added to any of the devices
that I used (Coralife
ozone reactor, straight into a skimmer, or my tubing
reactor), the ORP was never higher than this. Even when
used through the skimmer with no activated carbon treatment
of the effluent, the ORP was no higher. Consequently, I did
not need to use the ozone on a controller.
Was ozone being added? Clearly, yes. The water's ORP exiting
reactor measured 680 mV. I could also detect an ozone/OPO
residual of 0.1 - 0.24 ppm chlorine equivalents (details of
such test methods are provided in air
flow section of the previous article). So the ozone was
having the desired effect on the water in the reactor.
Would the ORP have risen more with additional ozone? Certainly,
yes. But using higher amounts of ozone causes more risk of
harm from overdose, and it may not further improve the primary
reason for using it: water clarity. More ozone might have
resulted in more disinfection of the water in the ozone reaction
chamber, and possibly a further reduction in dissolved organic
levels, but I am not sure that either of those is necessarily
Because many aquarists focus on ORP
levels when using ozone, a final repeated caution about the
inherent complications of ORP measurement is warranted, along
with some examples. ORP is not a simple measurement like pH.
The metal probe's tip is very sensitive to what is bound to
it, and it can take days for it to become coated with organics
and other materials in reef aquarium water. So, when the probe
is first put into a reef system, the ORP can drift for quite
some time as these processes slowly take place. Moreover,
every time the probe is calibrated or moved into a different
solution, it can again take days to re-establish itself in
For all measurements I used a Pinpoint
ORP probe attached to an Orion 710A pH/ORP meter. Proper
operation was checked using Pinpoint's 400 mV single-use calibration
Here are some examples of apparent ORP measurement complications:
1. After using ozone for several weeks in my system, the
ORP was running in the 300-330 mv range, depending on the
pH and whether I had recently cleaned the skimmer. Removal
of the probe for calibration with a commercial 400 mV fluid
(American Marine/Pinpoint) always showed about 410 mV after
30-60 minutes, which I decided was close enough.
Then the probe was used to measure the highly oxidizing
fluid exiting the ozone reaction chamber (680 mV) for 24
hours. Upon returning the probe to the aquarium, the ORP
was reading only 276 mV, and stayed at about that level
for several days.
Putting it back into another 400 mV calibration pack showed
the ORP still to be about 410 mV, as before. Then returning
the probe to the aquarium gave an ORP that slowly rose,
and after 24 hours was again above 300 mV.
I do not believe that the aquarium's ORP happened to be
unusually low right after exposing the probe to the highly
oxidizing fluid. I do believe that ORP probes can retain
a memory of what they have been exposed to, which is exerted
through changes in the organic materials bound to the probe's
surface. Exposure to different solutions, even calibration
solutions, can alter the nature of these bound organics
in a way that can impact the ORP that is measured for days
after the initial exposure.
2. Many aquarists find that ORP rises over many days to
weeks as the probe sits in their aquarium water. This rise
may be due to algae growing on it, releasing O2
and other oxidizing species very near the metal tip. These
aquarists find that gently cleaning the ORP probe often
causes the value to drop back to earlier levels. I have
not noticed this effect, but my ORP probe is kept in a totally
In summary, aquarists should be wary of over interpreting
ORP. Small changes may be caused by factors unrelated to ozone
use per se (such as pH or organics binding to the probe).
All ORP measurements ought to be viewed as having a relatively
large "uncertainty" when they are being compared
to other aquaria, perhaps on the order of +/- 25 ppm or more.
Changes observed in a single aquarium over time may
be more useful and interpretable than comparisons between
Increasing the water's clarity is
the primary reason that many reef aquarists choose to use
ozone. Most, but not all, aquarists report an increase in
their water's clarity after initiating ozone. Note that this
effect primarily reduces the yellowing of the water, and not
so much (although possibly some) the individually visible
particulates in the water.
In order to assess water clarity, I took pictures of an
off-white piece of plastic through the length of my aquarium.
I used a digital SLR camera (Konica Minolta 7D) which I could
set to a fixed color temperature. I took photos at settings
of 5500K and 9900K (I could not select 10000K). In the end,
the series of photos show similar changes, although one set
is obviously bluer than the other.
Figure 1 shows side-by-side pictures before and two weeks
after initiating ozone. The photographs were taken with the
exact same camera settings (9900K color temperature, same
focal length, f-stop, exposure time, etc.). Clearly,
the water was more yellow before the ozone was initiated.
Figure 1. Two digital photographs of a plastic
bar taken through four feet of aquarium water. The bar
on the left was taken before using ozone, and the bar
on the right was taken after two weeks on ozone. The
numbers were written onto the bar with marking pens.
All camera settings were identical.
Whole aquarium photographs do not show an apparent change,
and that difficulty has been noted by many aquarists who have
tried to show changes in water clarity. Before and after whole-tank
photographs (Figure 2) show little apparent difference. Nevertheless,
an improvement in clarity was visible to both my family and
me. While it was not as dramatic as some report, it was significant.
Figure 2. Overall photographs of my 120-gallon
reef aquarium. The top one was taken before adding any
ozone, and the bottom one was taken after two weeks
on ozone. All camera settings were identical.
I also tried to monitor light penetration by using a lux
(light intensity) meter on the bottom of the aquarium. Unfortunately,
the second to second variation and the variation in the reading
by very slight changes in positioning were larger than any
changes due to changes in water clarity.
A second potential way to gauge light penetration is via
the overall exposure of photographs. Figure 3 shows the aquarium
taken at a particular exposure before ozone (top) and at three
slightly different exposures after two weeks of ozone usage.
Rough brightness comparisons of these different photographs
suggests that the "before" picture has a similar
brightness to a slightly less-exposed "after" photograph
(between 0.67 and 1.00 exposure). Figure 4 shows a similar
comparison with an even lower exposure (0.5 times normal).
It clearly appears to be darker than the before photograph
at normal exposure. Consequently, while not especially quantitative,
this comparison is consistent with somewhat greater light
penetration in the post ozone situation. A similar comparison
and conclusion can be drawn from the brightness of the two
halves of Figure 1.
Figure 3. Overall photographs of my 120-gallon
reef aquarium. The top ones were taken before adding
any ozone, and are all taken with the same exposure
(as in Figure 2). The bottom series was taken after
two weeks on ozone, and is shown at three different
exposure levels (0.67x, 1.0 x and 1.33x).
Figure 4. Overall photographs of my 120-gallon
reef aquarium. The top ones were taken before adding
any ozone, and are all taken with the same exposure
(as in Figures 2 and 3). The bottom series was taken
after two weeks on ozone, and is shown at three different
exposure levels (0.5x, 0.67 x and 1.0x).
Aquarists have sometimes reported
a reduction in algae growth upon initiating ozone. Understanding
how this might happen, however, is somewhat difficult. If
oxidation with ozone were to make soluble organic materials
more biodegradable by bacteria, that might increase bacterial
growth. The bacterial growth might then result in a reduction
in nutrients as the bacteria consume them, as is often observed
when dosing organic carbon sources such as acetate (vinegar)
or ethanol (vodka).
However, the effect may also relate to more esoteric changes,
such as altering the availability
of iron or other nutrient metals (by altering the oxidation
state of the metal or the binding by organics). Such effects
were discussed in a previous
article. Nevertheless, the connection between such changes
potentially caused by ozone and algae growth is unproven.
Further, while some aquarists report reduced algae growth
when using ozone, many do not. In my tests I set up a photo
record that can be used to gauge the rate of growth. As I
did in a previous article which examined the impact of silica
addition on green algae and diatom growth, I took pictures
of the inside of the aquarium's front glass through its side
(Figure 5). Over time, algae grows, and the mirror-like interior
surface becomes clouded with it. Tracking this growth over
time allows me to gauge algae growth in the aquarium.
Figure 5. Photographs of the inside of the front
glass taken through my 120-gallon reef aquarium's side
panel before initiating ozone. The glass was scraped
clean and the pictures were taken later that day, and
then two, three and four days later, showing algae growth
on the glass.
Such a series of photographs was taken before initiating
ozone, and then after beginning the use of ozone (Figure 6).
It does not appear, from these photographs, that there was
any decrease in the rate of algae growth on the glass. Because
at that time I did not have what I would describe as problem
algae elsewhere in the main aquarium, I did not track any
other sites. The conclusion that ozone did not alter the growth
of green algae, however, is also consistent with my perception
of the main aquarium itself.
Figure 6. Photographs of the inside of the front
glass taken through my 120-gallon reef aquarium's side
panel two weeks after initiating ozone. The glass was
scraped clean and the pictures were taken later that
day, and then two, three and four days later, showing
algae growth on the glass. The progression is quite
similar to Figure 5, which was taken before ozone use.
At the time these experiments were carried out, an easily
observed patch of cyanobacteria growing was on the glass of
the 90-gallon aquarium in my basement. I monitored this patch
for several weeks, before and after initiating ozone. It was
growing slowly during this period, and continued to grow after
the ozone was started. It did not, as a few aquarists have
observed, decline perceptibly when ozone was started.
So my conclusion is that ozone did not reduce the growth
of algae or cyanobacteria in my aquarium. Other aquaria may
have different results, for example, by using more ozone to
reach a higher ORP, or having generally different husbandry
Response of Organisms
Some aquarists report visible changes
in large organisms upon initiating ozone. Some aquarists note
changes such as differences in coral polyp extension. I noted
no such changes in the various corals and other invertebrates
in my aquarium, including both hard and soft corals and a
large H. crispa anemone. In fact, no organism responded
visibly. Figure 7 shows some typical examples before and after,
taken both to monitor the organism's extension, etc., or to
compare its apparent color or brightness when photographed
under identical conditions. No differences in appearance were
noted in photographs or by my family and me. I also noticed
no reduction in the species known to feed on organics or particulates.
Figure 7. Photographs of three representative
aquarium organisms taken before and two weeks after
initiating ozone. No apparent differences can be noted,
either in attributes such as polyp extension or in their
Some aquarists, and even some ozone
equipment manufacturers, make claims about oxygen levels in
the aquarium being raised though the use of ozone. This claim
is potentially based on two things: the breakdown of ozone
and ozone byproducts to produce O2, and the fact
that many ozone reaction chambers cause air and water to mix
under pressure, potentially forcing more O2 into
the water. Using an ozone generator that supplies 100 mg/hr
(1.7 mg/minute) of ozone into an ozone reaction chamber with
a flow rate of 0.5 gallons per minute (2 liters per minute)
could theoretically raise the oxygen level by as much as 1.7
mg/minute/2 liters per minute = 0.8 mg/L = 0.8 ppm O2.
Of course, the generator may be producing less than its nominal
rating, and some ozone will be lost to the air. Nevertheless,
the potential is there for an oxygen rise in the effluent.
Many aquaria experience a drop
in oxygen at night, even if they seem to be highly aerated.
reefs show diurnal changes in oxygen levels, with a variation
of 7-8 ppm O2 for the daily high and 5-6.5 ppm
O2 for the daily low in some cases. In my case,
with large refugia lit 24 hours of the day, I do not see much
nighttime oxygen drop(although I've not measured with a high
sensitivity meter, but rather with an ordinary oxygen test
it), but the measurements that I've taken do suggest a small
drop (see below).
I obtained the following test results before and after using
ozone in my system:
Main 120-gallon tank just before lights on: 5-6 ppm O2
Main 120-gallon tank just before lights off: 6-7 ppm O2
Refugium 1 (always lit) just before main lights on: 6-7
Refugium 1 (always lit) just before main lights off: 6-7
Refugium 2 (always lit) just before main lights on: 6-7
Refugium 2 (always lit) just before main lights off: 6-7
Main 120-gallon tank just before lights on: 6 ppm O2
Main 120-gallon tank just before lights off: 7 ppm O2
Ozone tubing reactor effluent after activated carbon: 6-7
Sump just before lights off: 7 ppm O2
A strict reading of the values that I obtained suggests
a small rise of between 0 and 1 ppm in O2 in my
main tank. However, the kit is hard to read in the 5-8 ppm
range, so the oxygen could have risen by 0-1 ppm, or more,
or perhaps not at all. The effect, if real, may be much larger
in an aquarium where the oxygen drops much more at night (i.e.,
those without refugia lit at night or those with less aeration).
Effect of Air Drying
Many aquarists use air dryers to maximize
the effectiveness of ozone generators that use corona discharge.
I tested the effects of a Red Sea tube-type air dryer. I used
the 500 g model (there is a second model half that size).
In order to determine its impact, I measured ozone and ozone
in the ozone reactor's effluent before it reached the carbon.
For these experiments, I used my tubing reactor with a water
flow rate of 0.6 gallons per minute and air flow that was
very roughly a third of that (based on the relative volume
of air and water inside the tubing).
The relative humidity was measured in different locations
in my basement fish room to be 10-30% (higher near an open
refugium). The air temperature was 65-70° F in these locations,
providing a dewpoint of 40-50° F (5-10° C) The air
pump driving the ozone system was moved to these different
locations and kept in place while a residual oxidant (OPO)
measurement was made on the reactor's effluent (before the
activated carbon). The results are shown in Table 1.
1. Effect of air drying on ozone effectiveness:
in reactor effluent (ppm chlorine equivalents)
dryer 10 min. (dewpoint = 5º C )
dryer 30 min. (dewpoint = 5º C )
to 0.20 ppm
air dryer, freshly baked dry
dryer 30 min. (dewpoint = 5º C )
dryer 30 additional min. (dewpoint = 10º C)
From these data it appears that the dryer's impact was minimal
under the conditions tested. Perhaps this dryer is not very
effective at dropping the dewpoint to the very low levels
often discussed with respect to ozone generation (-30°
C to -80° C). Alternatively, perhaps the ozone generator
itself is not as sensitive to humidity as claimed in the literature.
In any case, the data here do not support the air dryer as
a critical piece of equipment.
Disinfection of Water by Ozone
In the first
article in this series I discussed how ozone is used when
disinfection is the desired end goal. I stated there that
I do not believe that most aquarists use enough ozone for
a long enough contact time to be particularly effective at
disinfection, although some bacteria may be killed in the
water in an ozone reactor. Now that I have measurements, we
can go back and see if this still seems true.
reactor, for example, was the most effective way that
I used ozone, with a typical measured exposure of 0.2 ppm
chlorine equivalents (0.14 ppm ozone equivalents) for about
45 seconds of exposure. When using a skimmer, this contact
time would be reduced to just a few seconds. I showed in the
article that exposure to 0.5 ppm ozone (unknown contact
time) in a seawater system did not reduce the bacterial load
in the system as a whole. In freshwater systems, where bacteria
are believed to be easier to kill because the ozone does not
so rapidly react with inorganic ions such as bromide, exposing
the water to 1.0 to 1.3 ppm ozone for 35 seconds reduced the
system's bacterial load by 40-90%. Here, the amount of ozone
used is nearly 10-fold lower, and it's seawater, so the reduction
is expected to be smaller.
Still, some of the organisms in the reactor may well be killed.
Yeast, for example, in freshwater at pH 8.5 are about 90%
killed after exposure to 0.45 ppm ozone for 45 seconds.1
Save a lot with the Publix Weekly Ad
grocery sale of this week.Here we have about one-third that amount of ozone, so at least
in freshwater, a significant portion of those organisms would
be killed. Dropping the contact time back to 5 seconds reduced
the killing effectiveness to less than 50%.
Activated Carbon Treatment
It is important to treat both the
air and the water exiting an ozone reactor before they are
released into the aquarium and into the room's air. In most
of the experiments that I ran, I used a homemade
GAC (granular activated carbon) column that treated both
the air and water at the same time. This treatment is accomplished,
as detailed previously, by inserting the tubing carrying the
ozonated air and water mixture a few inches below the surface
of an ~20" vertical column of GAC. The water passes down
the column and into the sump, and the air can escape by traveling
up or down the column through the GAC. When using the Coralife
ozone reactor, there are actually two tubes carrying effluent,
one carrying water and one carrying both water and air. These
were both treated as above.
The effectiveness of this carbon column for treating the
air is easy to establish qualitatively by odor. In normal
operation, no odor is detectable in the basement room where
my sump and aquarium equipment reside. A faint odor of ozone
can be detected by smelling directly at the surface of the
carbon column, but not otherwise. In my opinion, this level
of treatment provided an adequate reduction in ozone levels
to be acceptably safe.
However, if the tubing carrying the ozone reactor's effluent
is pulled up so that the water flows into the column but the
air simply escapes into the room, the entire basement smells
strongly of ozone. Consequently, during normal operation the
GAC is having the desired effect of catalytically breaking
down the gas phase ozone before it has an opportunity to escape.
In order to assess the GAC's impact on the water, the water
can be tested for ozone and ozone byproducts (OPO's)
before and after the GAC. Using my tubing reactor, with a
water flow rate of about 0.5 gallons per minute, I found that
the residual oxidant was 0.10 - 0.24 ppm chlorine equivalents
before the activated carbon. After the activated carbon, the
effluent had an oxidant level of 0.04 ppm chlorine equivalents
When using the Coralife ozone reactor as the reaction chamber,
the water flow rate was set to 0.44 gallons per minute, with
an additional 0.05 gallons per minute of water in the air/water
overflow. Both of these water streams were tested. I found
0.5 ppm chlorine equivalents in the air/water stream and 0.02
to 0.04 ppm chlorine equivalents in the primary water flow
before the GAC. The combined flow therefore would have a level
of about 0.09 ppm chlorine equivalents. After the activated
carbon, no oxidant could be detected (<0.02 ppm chlorine
Clearly, the GAC is doing a good job of reducing the highly
oxidizing species present in the water. In some tests it was
not perfect, but I believe that these levels (< 0.04 ppm
chlorine equivalents) are acceptable. Interestingly, the GAC
does not greatly lower the ORP. The ORP before the activated
carbon was 680 mV after 5-15 hours of equilibration, and was
670 mV after 8 hours of equilibration in the post activated
carbon effluent. Consequently, the effluent's ORP is not a
suitable way to measure whether the activated carbon is effectively
removing residual ozone and its byproducts.
Conclusions About Reaction Chambers
The Coralife Ozone reactor did not
impress me as an effective device to contact ozone with aquarium
water. It was difficult to assemble and reassemble, and after
a few times, the internal parts began to break apart. I also
could not get the air and water tubing attachments to be reliable
enough to justify using it, risking water spewing onto the
floor. Several times I accidentally bumped into it, and one
of the hoses popped off. While the large water lines could
be attached with hose clamps, I could not easily attach such
a clamp to the small air/water lines.
Using ozone with my skimmer was certainly easy to set up,
and would be largely free from any risk of catastrophic failure.
The two concerns with this setup are the large release of
gas phase ozone into my basement (indicated by the strong
odor) and the risk of embrittlement of my skimmer. Together,
these convinced me that this method was not a good option.
If the air could be collected and passed over GAC, then this
approach may be fine.
The tubing reactor that I described in the previous article
performed admirably. It attained more ozone/OPO in the overall
reactor effluent than the Coralife Ozone reactor, and has
a longer contact time. It is also largely fool proof, with
little that can clog or get dirty inside. It remains to be
seen how long the device will last, but high density polyethylene
is fairly resistant to degradation by ozone.
The one factor that remains to be fully worked out is the
GAC column used with the tubing reactor. The flow out of the
reactor is not steady, but rather comes in bursts of air,
then bursts of gas, with the flow rate varying considerably
over the span of even just a few seconds. It seems that after
running for a few weeks, the carbon can become too tightly
packed into it, and when the water flow peaks, the water can
overflow the column. A wider column, or a less tightly packed
one, may be preferable to prevent such overflows.
Details of My Aquarium System
In order to evaluate whether the effects
obtained in my aquarium will translate to other aquaria, it
is first important to understand how my aquarium is maintained.
The improvement in water clarity, for example, is likely to
be far less dramatic in aquaria already using a large skimmer,
lots of activated carbon and lots of water changes, than in
the same aquarium maintained using none of those practices.
Because real reef aquaria include both of those examples and
everything in between, it is incumbent on aquarists to decide
for themselves how their reef aquarium might relate to mine
if they want to use my results to predict what they might
find when using ozone. Nevertheless, there is a lot more information
in this section than many aquarists may be interested in,
so skipping this section may be appropriate for some.
My aquarium system consists of two main tanks (120 gallons
and 90 gallons) and a variety of support systems. The aquaria
contain a variety of fish, live rock, sand, and invertebrates,
including both hard and soft corals. In short, they are typical
"mixed" reef aquaria.
The fact that there are two aquaria in one system is not
important with respect to ozone use, but the total tank sizes
are relevant in order to evaluate the amount of ozone, activated
carbon, skimming, etc. that are used. Nearly all of the "in
tank" results contained in this article were for the
Water from these two tanks is sent through several refugia
and into a sump. The refugia consist of four water containers,
each with a surface area of 4-6 square feet (total about 21
sq. feet). In each refugium is a large amount of macroalgae
(primarily Caulerpa racemosa and Chaetomorpha
sp.) lit with a variety of lighting systems (one 175-watt
4300K metal halide lamp; eight 32-watt Phillips warm soft
white fluorescent tubes (F32T8/Soft White/K&B), and two
60-watt incandescent spot lamps). All bulbs except the spot
lamps are on all of the time. The spot lamps are on a reverse
light cycle to the main tank.
Two of the refugia have sand beds consisting of oolitic
aragonite about 6" deep. All of them contain live rock
and rock rubble. The sump also has a large amount of live
rock, and the whole system has roughly 500 pounds of live
rock in it. This rock was all wild, natural rock, mostly from
Florida and Tonga, and ranges in age from seven months to
more than 10 years.
The 120-gallon tank is lit by two 250-watt XM HQI double
ended 10,000K metal halide lamps on a PFO HQI dual ballast.
The bulbs are in PFO HQI Mini Metal Halide Pendant fixtures.
The main tank is also lit by four Coralife Aqualight Mini
PC Fixtures. The power compact bulbs are all 9-watt, and there
are three 10000K lamps and five actinics (two bulbs per fixture).
There is also a moonlight run by a Tunze controller.
The 90-gallon tank is lit with two 175-watt 10,000K metal
halide lamps on electronic ballasts.
Water motion in the 120-gallon tank is provided by the two
sump returns and two Tunze 660 powerheads on an electronic
controller that varies the intensity of each over time. In
the 90-gallon tank, water motion is provided by the sump return
and a Hagen 802 powerhead on a Tsunami wave timer.
The water is skimmed with an ETS 800 Gemini skimmer driven
by an Iwaki 55 RLT pump. All evaporated water is replaced
with limewater that is usually less than saturated. I replace
approximately 1% of the water volume each day automatically
using Instant Ocean salt mix that has been boosted by 70 ppm
calcium using Dowflake
calcium chloride and 150 ppm magnesium using MAG
flake magnesium chloride. I also normally add silica
to the system. The silica is for sponges, diatoms, snails,
etc., and the iron is for macroalgae growth. The silica additions
were suspended during the ozone experiments as it can alter
the apparent rate and type of "algae" that forms
on the glass. The iron was continued as usual.
The fish are fed three times a day with a variety of frozen
and dried foods, and this routine was fixed during the period
of the experiment.
The pH usually runs from 8.3 to 8.5. Nitrate and phosphate
are typically not detectable with Hach and Salifert kits.
The salinity is approximately 35 ppt. Alkalinity is usually
3-4 meq/L (8-11 dKH) and calcium is about 420-450 ppm.
All things considered, the ozone provided
a small but significant increase in water clarity. While it
may also be providing other benefits, I have been unable to
show them definitively.
My concern with using ozone, aside from its initial capital
expense, has been to protect both my aquarium inhabitants
and my family from any harmful effects of ozone or its byproducts.
Using the equipment described above (especially the activated
carbon treatment of both the water and the air to remove ozone
and its byproducts), I am satisfied that the system I use
is adequately safe on all accounts.
Because of the safety issue's resolution and the water clarity
effects, I believe I will continue to use ozone with my tubing
reactor and GAC column. I will probably not bother to continue
to use the air dryer, but when the humidity is highest later
in the summer, I may again compare the relative effectiveness
of the ozone generation with and without the dryer.