Quoted from artice regarding skimmer efficiency and ozone use
For years, many people have suggested that ozone improves skimming efficiency. But does it really? Whether one uses a skimmer or not, the introduction of ozone into water that contains organics will have a big impact on those organic molecules. Nearly any organic molecule can be oxidized in the presence of ozone. One common effect of oxidation is the elimination of the types of molecules that lead to the adsorption of visible light. Compounds containing conjugated double bonds are one of the most common natural chromophores. These molecules are, however, very susceptible to oxidation to uncolored species.
It is thus highly probable than any elimination of yellow coloration in a marine tank on using ozone is due to the simple conversion of the organics from a light absorbing form, to a nonabsorbing form. The organics are not removed by a skimmer, and are not completely destroyed. They are just in a different form. Whether that is desirable or undesirable will depend entirely on the specific organic compounds in question.
The follow-up question is whether these oxidized compounds are more susceptible to being removed by a skimmer than before oxidation. At present, I am not aware of any study which shows that they are, or even of any physical reason why the would be. In general, oxidation makes organic molecules more hydrophilic. In some cases, it also breaks molecules into smaller pieces. Neither of these actions should lead to greater skimming. Hydrophobic molecules (in the presence of amphipathic molecules) are easily skimmed. Converting them to amphipathic molecules through introduction of a hydrophilic group will mean that they are still skimmed, but not that they are easier to skim. Oxidizing amphipathic molecules is also unlikely to increase skimming, and if they are oxidized so much that they become completely hydrophilic, then they will not be skimmed at all. I cannot think of a single molecule which becomes easier to skim by oxidation. On balance, there does not appear to be any evidence that the use of ozone increases skimming efficiency per se. That is not to say that ozone has no effect. The use of ozone can certainly lead to fewer yellowing compounds in the water, and might make many organics more susceptible to biodegradation. It can also sterilize water if used in sufficient concentrations. Are these things desirable? That's up to each aquarist to decide.
