Ozone gas is a highly useful addition to any re-circulatory filtration system and although widely used in marine systems, it also has uses in freshwater applications. 

Ozone (O3), consisting of three oxygen atoms, is highly reactive and has many uses:

  • It is highly effective in removing organics, pesticides, dyes and ammonia and nitrites. 
  • It reverts to oxygen quickly, leaving no detrimental residues when used correctly. 
  • It is economical and non-polluting when used correctly. 
  • It can be used as a sterilising agent to control viruses, bacteria and other pathogens, before, during and after water is used for re-circulation. 
  • Ozonisation improves biological and mechanical filtration. 
  • It can remove biological oxygen demand and raise REDOX potential in the water. 
  • It can oxidise long chain molecules, which cannot be achieved by biological filtration alone. 
  • Smaller bubbles can be produced in saltwater than in freshwater. As small bubbles have a higher surface area to volume ratio than big bubbles, they are more efficient at injecting ozone into the water.

Advice on using Ozone

  • Ozone is very unstable.  It will revert to oxygen within about an hour, even if there are no organics in the water for it to oxidise. 
  • Use clean dry air or oxygen to produce ozone. Humidity can reduce ozone production by up to 70% and can form scale and nitric acid in the generator which will significantly affect its efficiency.

Where to apply Ozone 

  • Ozone should be used in a protein skimmer in marine systems. Ozone gas helps the protein skimming process, while the vessel allows the capture of the off gas for venting. Ozone works very well in gas saturators for freshwater systems, as well as in more recently available freshwater protein skimmers.

Ozone Technical Information 

Ozone should be applied on an individual tank basis at the equivalent of 5-15 mg/hour per 100 litres of volume.  In commercial applications, 0.05mg ozone per l/hr of flow is sufficient to achieve a recommended redox of 250-400mV. (In freshwater you will generally achieve a lower redox of 250-350mV mainly because of the bubble size).  A much higher dose rate of 0.2-0.5 mg of ozone per litre of flow is required to achieve redox levels of 700-800 mV, at which level the water can be considered sterilised but unfit for livestock without further treatment.


  • CAUTION: Ozone is dangerous and should be used with care. Full Ozone Health & Safety leaflets are available from TMC - please ask for details. 
  • Ozone must never be introduced directly into the livestock tank and a suitable reactor should always be used. 
  • Ozone should be introduced slowly into the system and monitored carefully to ensure that no negative effects occur. 
  • A redox controller should be used which will automatically adjust the ozone generator to changing conditions. 
  • Off-gas from reactors should be directed outdoors or through a suitable ozone destructor device, such as UV light or activated carbon. 
  • For ozone generators of 2g/hr or more, it is recommended that an atmospheric ozone monitor is used. 





Ozone Generators