Ozone can be used in aquarium as it is already commonly used in wastewater treatment plant as in Koi pond. Due to its oxidizing capabilities, ozone can break down harmful waste products produced by fish. In a marine aquarium (or in a freshwater tank with pH higher than 7.5), ammonia is efficiently oxidized to less harmful nitrite and further to nitrate. This oxidation reaction can also be performed by bacteria in a biological filter. Another important property of Ozone is its sterilizing ability. Harmful bacteria and other possible pathogens that float in the water are efficiently killed by ozone. The oxidation reduction potential (ORP) is a measure of the relative oxidizing power of the water. Typically O3 raises ORP and it is important to monitor this paramter or have a way to reduce it before to bring back the water in the system.
Here are few ozone generator (or ozonisers) for fishkeeping:
Since I am fan of Aqua Medic brand and had few years ago a previous version, I picked an Aqua Medic Ozone 90, generating max 90mg O3 / hour. A more performant generator is not necessary a better choice.. It is recommanded for 100L of fresh water to target 5mg/h up to 25mg/h in some cases. Our tanks are 540L -> ~25mg/h. If you take the Ozone 250, then 1/10th of electronic controller stands for 25mg/h.. and the control is then not ideal. Therefor Ozone 90 is the best for us.
In additions, parts list:
Aqua Nova Bio Balls, simply to increase air / water contact surface
Aqua Medic grid plate, ideal divider to keep bio balls in proper tubing section
U-PVC male/female solvent adapter, male thread 50/63 x 1 1/2"
U-PVC solvent union 50mm
U-PVC solvent tee 90° with one male/female socket 32 x 32 x 25/32mm
U-PVC solvent reducing bush m/f 50 x 32mm + 25 x 20mm
U-PVC hose tail with male solvent socket 20 x 8mm + 25 x 12mm
Evolution Aqua evoUV connector need to be cut
Grid plate need to be cut just to fit inside the transparent tubing
Just about 8 bio balls will fit inside the tubing
All need to be glued together, take care to dry test before to insure all parts fit
Here is the final product, directly mounted to the UV sterilizer connector. You can tune it with a little angle slighlty counter-clockwise on below montage, in order to the air + ozone in the UV chamber to accumulate a bit before to go back into the sump. This way, O3 has time to be neutralized..
UV makes a great difference: ORP is more than 400mV with UV off, less than 40mV with UV on.
Finally, short videos about this topic.