Every hobbyist's challenge is to keep a good looking aquarium, and all such tanks are typified by high redox potential levels. Increasing the redox should, therefore, also be on your list of priorities.

Many factors must be combined to achieve and maintain high redox potential levels, and all are within the reach of the average hobbyist. There is no magic to it. It is not complicated and does not require years of experience or special schooling. Often common sense combined with the right equipment will do it for everyone who tries. Let's review a few that I recommend:

Reef aquariums that are operated without a protein skimmer will greatly benefit from the addition of such a unit. Size it correctly, so you do not find yourself operating a unit that does not do the job for you. Columnar skimmers can be very efficient at removing organic material that would otherwise pollute the water and tax the filters.

Checklists on how to size the right filter for your tank are available, and will tell you exactly what the correct one for your tank is. Sometimes you will hesitate between two units, I suggest that when in doubt you buy the larger unit. The best skimmers, at least the most efficient ones, are venturi operated skimmers. They have the additional advantage of not requiring an air pump and also not requiring air stones. Not all venturi skimmers can be operated with ozone; if you plan to use it make sure you buy a unit that can.

The principle behind skimming, or foam fractionation as it is better called, is that if you remove organic and other material from the water by using a device to do so, that material can no longer break down in the tank and pollute the water, because it is no longer part of your system.

Typically, adding a protein skimmer to an aquarium that was not equipped with one will raise the redox potential by 75 to 100 mv (Pieters, 1985). If ozone is used in addition to the regular skimming, the redox can be raised even further, and the level is really only limited by the amount of ozone used.

To run a protein skimmer efficiently you must follow certain guidelines, here are a few:

• Flow at least 1 to 1.5 times the content of your tank through the skimmer, per hour. More will usually not hurt, but may not be necessary.
• In columnar skimmers a large amount of air must be blown into the column by means of a strong air pump. I particularly recommend the Wisa 200 and Wisa 300 air pumps. I use them myself and have done so for many years.
• Columnar skimmers operate with air stones. They must deliver real small bubbles for the skimming to occur efficiently. Air stones wear out rapidly. Change them about every 3 to 4 weeks. Use limewood or oak. The latter make even smaller bubbles than limewood ones, but offer a far greater resistance and can only be operated with real strong air pumps.
• In venturi skimmers no air pump and no air stones are required, but you must clean the venturi valve itself from time to time. Every week is probably a minimum. Salt creeps up inside the valve and reduces its ability to suck in air forcefully. Use a pipe cleaner or a small brush.
• Tanks operated without a skimmer will not show immediate results when one is installed. G. Bepko (1987) reports that it can take up to 2 weeks or more for a significant change to become apparent.
• If ozone is used, make ozone safe connections between the ozonizer and the skimmer input, to prevent the ozone generated by your ozonizer from being used up in the chemical reaction between the ozone and the materials used. Such is totally counter-productive and is the reason Norprene* hose is recommended.
• Prevent the ozone from entering the main body of water in your tank by flowing the water coming out of the skimmer over activated carbon. Use a residual ozone test to make sure no ozone can find its way into the tank itself.
• Ozone should not be allowed to enter your biological chamber because it will destroy your bacterial filter.

S. Spotte and M. Moe in their books _Seawater Aquariums, A Captive Environment_, respectively The Marine Aquarium Reference go into great detail about how to set skimmers up and how to run them. You may wish to refer to those books as well.

Permanganates are very strong oxidizers which can be used to rapidly increase the amount of oxidation that takes place in the tank. In the process your water will be cleaned up. Because of their high potency you must be extremely careful when using them. You can do more damage than good if you are not.

Always follow the instructions that come with the product carefully and do not overdose under any circumstances. Permanganates raise the redox potential very rapidly and can, in the process, make the environment so harsh that your fish, corals and invertebrates will suffer greatly.

Pure potassium permanganate comes in purple crystals that are hard to handle in small quantities. It is very easy to use too many of them. If you resort to permanganates use a product that is not 100% straight, or use the liquid form that has been redox stabilized.

As you add permanganates a purple color will first develop. As the oxidation proceeds, this will turn to a brown slime or tinge depending on how long you use them for. The residue from the oxidation, and the color, can both be removed by water changes, by your mechanical filters, and with activated carbon. Skimmers will also remove the by-products of the oxidation efficiently.

Use permanganates only when all other methods have failed. Do not overdose and do not use them continuously. Permanganates are not a product meant to be used on a regular basis, but a palliative for situations that have gotten out of control. Talk to the manufacturer if you are not sure about the dosage and the way to introduce it into the tank. Don't take any chances. Get informed.

One of the better ways to increase the redox potential, but a method that requires the hobbyist to be careful, as we have seen earlier in this book. The problem most frequently encountered is that the hobbyist is at a loss when it comes to how much ozone needs to be used.

As I have stated earlier, the amount of ozone used is not the issue. The issue is that whatever that amount is, it must be used in such a way that no ozone is found in the water in the tank. Removing it efficiently from the water coming out of the skimmer, or from the ozone reactor is what the hobbyist must focus in on. Activated carbon and a residual ozone test will allow this to be done.

Additionally, a point will come where the water quality is at the level that the tank requires, as we shall see later in this chapter. When that point is reached, the amount of ozone needed to keep it there will stabilize itself. Indeed water of high quality does not require a lot of additional ozone to remain at that level. At such time the hobbyist must limit the ozone input by either using a redox potential controller, or by operating the ozonizer on a timer. In such cases a pen-type redox meter of good quality is really an instrument that the hobbyist should acquire. Coralife should have such a unit available for a very affordable price, by the time you read this book.

Another of the additives that increases both the oxidation and the redox potential of your tank's water is Iodine, usually available in the potassium iodine form. It is used for a totally different purpose however. Iodine is needed by all living things and especially by macro-algae. It is removed rapidly from the reef tank by protein skimming and ozone, as pointed out again, recently, by Moe (1989).

Because it is a required nutrient some hobbyists add it as supplement, which is fine and should be done on a regular basis. The danger resides in the fact that one can overdose rather easily on iodine and make the redox potential rise too fast. Follow the instructions on the bottle that it comes in carefully.

Do not use Iodine as a redox potential altering additive. Use it only as a supplement required because it is a nutrient. Use any or all of the other methods to alter the redox potential.