As we have been discussing, ozone must be used properly in order to avoid damaging the aquarium inhabitants (or the aquarist himself). To put it bluntly, high levels of ammonia exposure will kill the aquarium fish and invertebrates, as well as destroying the beneficial nitrifying bacteria that carry out biological filtration. Death from ammonia exposure is typically the result of asphyxiation, since the oxidative ability of the ozone damages red blood cells in several ways. Ozone exposure induces hemolysis of red blood cells, formation of methemoglobin (rendering the erythrocytes unable to transport oxygen), and red blood cell membrane lipid peroxidation.
Respiratory distress is therefore the early symptom of ozone exposure at low levels. Labored breathing, huffing, rapid respirations, and pallor are some early indications of ozone exposure. At higher levels, the gill tissue itself can be oxidized or "burned" by exposure to ozone, and critical damage to the gills hastens death.
This is what I usually advise home hobbyists with regard to ozone, Tom:
Ozone (O3) is the highly unstable triatomic form of oxygen. The instability of the ozone molecule makes it highly reactive, and it oxidizes or "burns up" organic compounds and microbes on contact. As a result, ozone is widely used for water purification and sterilization, particularly in Europe (Fenner, 2003a). When used in conjunction with a protein skimmer and properly administered, it provides many benefits to the aquarium and is a very useful option seahorse keepers should strongly consider employing.
Ozone chemically degrades large organic molecules, thereby helping to raise pH, increase dissolved oxygen levels and Redox potential, and improve water quality in general while greatly increasing the efficiency of your protein skimmer (Fenner, 2003a). Its ability to destroy microbes on contact also makes it a very useful disease control measure. Virtually all the large public aquaria employ ozone in their systems for these reasons.
For best results, an ozonizer or ozone generator is used to introduce ozone into the bubble column of a protein skimmer or a special reaction chamber. The outflow from the skimmer should then be discharged into a filter or sump for degassing and chemical filtration before being returned to the main aquarium (Fenner, 2003a). In the best systems, ozone is used in conjunction with an ORP controller in order to optimize and stabilize Redox (reduction-oxidation potential).
Ozone is not necessary for keeping seahorses successfully. Protein skimmers can certainly be operated effectively without it and captive-bred seahorses will thrive in a well-maintained system without the use of ozone. But in my opinion, the benefits ozone provides far outweigh the costs and it can be a very useful addition to a SHOWLR tank. Ozone is by no means a necessity, but it is a very worthwhile investment in the long-term health of your seahorses.
Best of luck with your ozonizer and ORP controller, Tom.