Thiel Book - Chapter 8 Page 3
THE MARINE FISH AND INVERT REEF AQUARIUM
Albert J. Thiel
Continued from page2
8.5 OZONE AND OZONIZERS:
Until Sander of Germany introduced ozonizers for use on home aquariums, only large systems were being treated with ozone to improve the water quality. Hobbyists might have read about the possible use of ozone and its beneficial effects, but that is about where it stopped. Things have changed quite a bit, indeed, nowadays American made units are available from at least two manufacturers.
Ozone is a special form of oxygen, an allotropic form. It has an extremely high oxidative power (over 2700 mv redox) and can, therefore, be used to our advantage to clean up the water in our tanks. Ozone oxidizes many unwanted compounds, especially organic ones, breaking them down into different compounds that do not affect the water quality as much as the original ones, or can be removed, for example, by protein skimmers.
By oxidizing compounds completely, some only partially, ozone greatly assists in the mineralization of many organic compounds present in the water. Mineralized compounds are complex compounds broken up in simpler forms, most of which are not as noxious as the original compounds themselves. Some of those mineralized compounds are then reused by the tank's lifeforms, or removed by other forms of filtration.
Because of its very high oxidative power, ozone can do as much damage as it can do good if it is not used properly. Many hobbyists refrain from using it because they are afraid it will kill off everything in their tank, or will damage system components. In fact, when ozone is not used with care and knowledge of what it can do, it may do both.
I am certainly not trying to scare you and suggest that you should not use ozone. I am not trying to depict a bleak picture of all the harmful results that ozone can bring about if used without care.
On the contrary. I am a very firm believer that ozone is a must on a reef tank and that it has to be part of the overall filtration of such a tank. It is highly unlikely that you will be able to attain, and maintain, the high water quality parameters necessary for a reef tank without using ozone. But you must know how to do so safely before resorting to its use.
My premise is as follows: use as much ozone as you wish, as long as no ozone is present in the water in the tank itself, and as long as it cannot find its way into the biological chamber of your trickle filter. Best is when using ozone to control the unit producing it by means of a redox potential controller. I said best, not required. Use ozone resistant materials wherever they are required, especially the hose between the ozonizer and the skimmer must be of ozone resistant material.
Always take the following into account when injecting ozone into your system, and check some regularly if necessary:
- All tubing that transports air and ozone mixtures must be totally ozone resistant. Norprene* (not the same as Neoprene*) and Polysulfone are the two recommended types of tubing to buy. Such tubing is more expensive, but you will gain by using them in the long run, as you will not only not have to replace tubing constantly, but you will be injecting all of the ozone produced by your ozonizer into your skimmer, without loss of ozone because of the chemical reaction taking place between the tubing and the ozone. Other types of hose will either harden, crack and leak ozone in the air, or will disintegrate in a matter of weeks, or a few months at best. Regular airline tubing does not do the job at all. Flexible PVC tubing, e.g. Tygon*, will give several months of service.
- All parts of your system that come in contact with ozone must be either ozone resistant or made of material that can resist ozone for a long period of time. This applies mainly to the protein skimmer you use. Not all skimmers will resist ozone's action for extended periods of time. Be especially concerned about small fittings used to make connections, and tubing that conducts the ozone to the air stones that are used in columnar skimmers. Viton* and polypropylene offer a good life expectancy. ABS and similar resins (often black) do not.
- No ozone should ever be present in the water in the tank. All ozone that is present in the water coming out of your skimmer must first be removed by means of a good quality activated carbon. You must flow the water coming out of the protein skimmer, or ozone reactor, over such carbon before it is remixed with the main water mass in the sump and tank. Change the carbon on a regular basis. I do so once a month. One pint of carbon is enough, but you must remember to change it.
- Test for residual ozone on a regular basis, using one of several tests available in the hobby. Most pool O.T.O kits do not work on salt water. They are meant to test for chlorine, not for ozone. They contain hydrochloric acid in addition to the O-Tolidine which is used to test for the presence of ozone. Although residual ozone tests and chlorine tests use the same makeup chemicals, they are used in different proportions, resulting in the tests not being interchangeable. Pool tests will not indicate the low levels of ozone that you are concerned about. As little as 0.02 ppm on a continuous basis is harmful.
- Always use an ozone safe check valve in line with the hose going from the ozonizer to the skimmer, or reactor, in which ozone is injected. Such check valves cost a fair amount of money. The main reason they are so expensive is because of the materials that they have to be made up of, to make them ozone safe and resistant. Ozone is a very strong oxidizer, remember. An $8.00, or so, check valve will not do the job, believe me.
- Place the ozonizer higher than the water level of the device in which you are injecting the ozone. This will protect the unit and especially its electrical parts. Always clean up water that may have gotten onto your ozonizer during maintenance, or water changes, immediately. Remember: your ozonizer is an electrical device. Water and electricity do not mix. Salt creep on the ozonizer will lead to electrical shorts, because salt conducts electricity when moist.
- Should the fuse in your ozonizer fail, replace it only with a fuse of "the same strength" as the one in the ozonizer. If it fails again within a short time (seconds to hours), it is likely that your ozonizer needs servicing. Do not attempt to fix it. Call the manufacturer and make arrangements to send it back. Most ozonizers work on very high voltage, several thousands of volts in most cases. Unless you are an electrician you are not qualified to deal with such current. Again, do not put larger fuses in the unit. Such can be very dangerous. Ozonizers are touchy devices and prone to more than an average number of failures. Get one with a long warranty. TAT, for instance, offers a 24 month warranty on theirs. See their warranty card for more details.
- You do not need an ozonizer with an output adjustment. In my experience they fail in a short matter of time anyway. Rheostats used to do so, do not seem to hold up for very long when used on ozonizers.
- If your unit is sized properly ozone output wise, you will need to operate it with an air dryer. Indeed, moist air - and around an aquarium the air is always very moist - will only allow you to produce about 40 to 50% of the rated output of your unit. My suggestion is, and has been for a long time, that hobbyists should get a unit that is rated for about double the amount of ozone they really need. Even when such a unit is then operated without an air dryer, it will still produce enough ozone.
- Ozone is a very pungent gas. You can smell as little as 2/100 ppm in the air. To prevent ozone from escaping into the air one can use a so-called "ozone cap" which is placed on top of a columnar skimmer, or a bag of activated carbon placed over the collection cup of a venturi skimmer, or both. Activated carbon traps ozone very effectively. Remember to change it from time to time.
- If you still smell ozone, even though you are using activated carbon in the way just described, suspect a leak somewhere, and check for such leaks and cracked tubing in the lines bringing ozone to your skimmer or reactor. If the ozonizer itself is at fault, send it back to the manufacturer for repair or exchange for a new one.
- Because ozone increases the water quality easily and can do so substantially in a short period of time, many hobbyists nowadays use redox potential controllers to switch the ozonizer on and off at preset levels of redox potential. Such is safer in the long run, especially if you are using a very strong ozonizer. It is, however, not an absolute requirement. Why redox potential controllers? Because the level of that redox potential, as we shall see in a later chapter, is a very good gauge of the quality of the water. The higher the number, the higher the water quality is.
Ozone has had a poor reputation in hobby circles for some time. The main reason is that those using it, either did not fully understand what ozone does, or did not know how to prevent it from ending up in the tank's water. As a result, many problems occurring in a tank on which ozone was used were blamed on ozone. Often, ozone was not even closely to blame. It just made for an easy explanation for problems that otherwise were hard to figure out. Knowledge and understanding are important, not only when it comes to using ozone, but in all areas relating to your tank. Read up on ozone in other books as well, and ask manufacturers of ozonizers as many questions as it takes for you to feel comfortable with its use. The more you know about ozone, the safer you will feel using it, and the less likely you are to have problems.
As the redox potential rises, meaning as the water quality improves, you will need less ozone to keep the water quality at that level. If you need less ozone, you must have a way of controlling its input. If you do not own a redox potential controller that may sound impossible. It is not. Use a timer that allows for on/off settings of 15 or 20 minutes each, and adjust the on/off timing until you can keep your redox potential within narrow bounds. This may take a little while for you to figure out, but it can be done. Allow for 6 to 8 hours to do so. Do it on a vacation day, or on a weekend when you have all the time needed to safely adjust the ozonizer/timer combination. It will be a lot less expensive than buying a $500.00 or so redox potential controller, unless you are ready to do so. It is a trial and error method, but if you take the time you will soon have it right.
