1.4 What is Redox (ORP) Potential?
In every chemical reaction electrons are transferred from one substance to
another. The substance that receives electrons is said to have been oxidized,
while the one that loses electrons is said to have been reduced. In freshwater
and sea water, many of these so called redox reactions occur simultaneously.
Because of the constant exchange of electrons the amount of prevailing
oxidative or reductive reaction can be measured as a voltage, by means of a
platinum electrode and a volt meter. This millivoltage is called the redox
potential also called the ORP (Oxidation Reduction Potential). The higher the
redox potential, the greater the oxidizing capacity of the water. Redox potential
values of between 300 and 350 mV (recommended as the desirable level)
indicate an oxygen rich environment with a low waste material content. The
redox potential can therefore be used as an indication of the quality of your
Aquarium environment.
Some authorities advise maintaining a redox potential of 400 mV or even
higher. Be extremely careful with high redox levels, values higher than 430 mV
can be dangerous, values of 600 mV will cause increased levels of sterilization
which should not even be considered for aquarium use.
Values below 200 mV indicate an accumulation of organic wastes and a low
oxygen level. Negative redox potentials are also possible indicating anaerobic
conditions which can occur, for example, under the bottom gravel.
1.5 The Relationship between Ozone use and Redox Potential
As Ozone is applied to aquarium water it will raise the oxygen level and break
down organic wastes i.e. sterilizing the water thus raising the redox potential.
Since too high a redox potential is as undesirable as a low redox potential it
is advisable to keep the redox potential stable by means of applying ozone
when the redox potential is lower than the desired value and switching off the
ozone when the upper limit of the redox potential has been reached. This can
be achieved by combing a Redox controller with the AquaZone (Ozonizer) unit
or using the AquaZone PLUS (combined Ozonizer and Redox controller). If ozone
is to be applied without the benefit of a redox controller the dosage should
be set at a low value so as to prevent too high a redox potential forming in
the aquarium.
2. Additional Equipment
In order to operate the AquaZone/AquaZone PLUS you require the following
equipment :
1. Air Pump.
2. Air Dryer – Recommended.
3. Ozone Reactor and /or Protein Skimmer.
4. Carbon filter – Recommended.
5. Redox controller. (Integral part of AquaZone Plus)
6. Redox (ORP) electrode. (Supplied with AquaZone Deluxe)
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3. Special Instructions and Safety Precautions for using Ozone
3.1
Ozonized air should be prevented from escaping into the room; it is advisable
to install a carbon filter on your protein skimmer or ozone reactor where
ozonized air escapes.
3.2
Do not let the redox value exceed 400 mV as harmful substances can be
produced which could damage sensitive organisms. The aquarium inhabitants
should be protected from exposure to free ozone and /or oxidation products.
The recommended method to remove any residual free ozone and any free
oxidation products is by vigorous aeration followed by filtration through
activated carbon. After this treatment the amount of residual ozone should
be checked regularly – maximum 0.05 mg per liter. (Recommended: Red Sea
Fish Pharm’s Residual Ozone Mini-Lab Test).
3.3 The Ozone production is affected by the humidity and dust content of the
air supply. Use of an air dryer will ensure a consistent ozone output and
longer equipment life. Strictly follow the manufacturer’s directions in servicing
the dryer media.
3.4 All air tube connections should be secured tightly.
3.5 The AquaZone unit should preferably be installed above the aquarium; in this
way no water can siphon into the unit in case of a power failure. If the unit
is located under the water line of your aquarium, you should install an ozone
safe non-return valve (not supplied with the unit) on the air tube connecting
the ozonized air to the reactor.
3.6
Ozone treated water should not flow back into the biological wet-dry filter
since the nitrifying bacteria are extremely sensitive to residual ozone. Even
amounts less than 0.05 mg per liter can adversely affect your filter bed.
IDEAL OZONIZATION CONFIGURATION
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