Most of the remarks already outlined in the pH meter and controller section apply to these instruments as well. In fact perhaps more so, because redox potential is a more difficult to measure parameter of the water quality. It is certainly a more misunderstood one, and one that is only recently beginning to find a good following amongst hobbyists maintaining reef aquariums.

Thiel (1985) was perhaps the first one to point out its usefulness in judging the water quality of aquariums, in the United States, in articles written for magazines, and lectures given to aquarium societies. Obviously others in the hobby, in the more professional end of it, have suggested the use of redox potential at earlier dates. Thiel (1986) introduced the redox potential concept to the hobbyist market, and offered the first redox controllers for sale in the hobby in the United States on a large scale, the ATK model from Klaes Aquaristik. In all fairness, Sanders of Germany had such a meter/controller available for some time before that, but had not been promoting its use very widely, even though their ozonizers had been around the United States for some time, and were being used in Germany in conjunction with those controllers.

As more literature that explained redox potential in greater detail became available, its measurement became more widespread and hobbyists started installing meters and controllers on their aquariums, especially on reef tanks. Little by little more brand names appeared on the market, to the point where the choice offered to the hobbyist is now rather large. Prices have started to come down as well, and excellent controllers can be bought for less than $ 500.00.

A separate chapter of this book deals with redox potential at length, and even includes the results of an experiment in redox potential control. Martin Moe in The Marine Aquarium Reference is an excellent source for more information on redox potential as well. In the literature you will sometimes find references to ORP, or oxidation reduction potential, rather than redox potential. They are both the same concepts, just different names. Redox is used mostly in Europe, and ORP more so in North America.

Because redox potential is such an accurate gauge of the water quality, hobbyists should take the time to familiarize themselves with its concept and meaning, as well as how it can be used to effectively improve the living environment that a reef aquarium is. A good deal of information on redox potential can also be found in _Advanced Reef Keeping Made Simple (I)_ and in Reef Aquarium Basics, both by A. Thiel as well (Aardvark Press).

4.5. CONDUCTIVITY METERS AND CONTROLLERS:

Conductivity is used by a number of more advanced hobbyists as an indication of the salinity of the water. Even though such is a much more accurate way to monitor salinity or specific gravity, we only recommend it in systems that are very automated. For example, conductivity controllers with two, rather than one, relays can be used to automatically dispense fresh water when the salinity is too high, and brine when the salinity is too low.

Such systems are very easy to set up, and were it not for their high price, they should be part of every good marine reef setups. More details on installing such an automated salinity control can be found in my other book: Advanced Reef Keeping Made Simple (I), available from Aardvark Press (published 1988, 440 pages).

Because of the type of equipment needed, the typical price of such a setup is around $900.00 to $1,000.00. If, however, you want full control, that is the way to go. All is relative, and if you have a system that houses several thousand dollars worth of fish, corals and invertebrates, such an expense can be very justified. Alternatively, if you travel a lot, and cannot rely, or do not want to rely, on someone else to take care of your system, a conductivity controller in addition to a similar unit for pH and redox, will take all the guess work out of running the tank, and will greatly increase the stability of the system. And stability is the one factor that is very important, and common to all successful reef setups that I have ever seen.

4.6 COMBINATION pH AND REDOX CONTROLLERS:

Although I used to favor such a double function instrument, and offered some for sale through my own company, I have recently changed my recommendation. I now strongly suggest the use of two totally independent controllers. One for pH and one for redox potential. The main reason for this is simple: when two units are housed in one and the same enclosure, and when something goes wrong with one of them, you must send in the whole unit for servicing. In the process you lose the use of both controllers, not just one. This can have dire consequences for an aquarium that is running well, and may contain very valuable livestock, especially if the servicing takes weeks, which is often the case, as some may have found out.

Moreover, it has been reported that interference between the two circuit boards can also be a problem in such units, even in micro-processor based ones. As a result I have switched my own system to independent controllers, and recommend that you do the same, especially if you are in the market for instrumentation.

4.7 TEMPERATURE METERS AND CONTROLLERS:

Meters are used to obtain information about many parameters associated with the water quality in the tank. Controllers are used to both measure, and take action, if the tested values requires such action. Stability in the reef tank has always been one of my main concerns, especially since time has proven that the more stable the environment is kept, the more successful the aquarium will be, providing, of course, water quality is at generally recommended levels.

Temperature is one of the many parameters that must be controlled, primarily because the animals kept in the reef are not accustomed to great variations in temperature, and will only do well in a very narrow range to boot.

There are few temperature controllers available in the hobby. The ones that you want to consider are, however, advertised in the magazines. Select a unit with a high degree of accuracy. Call the manufacturer if the value is not advertised. Check the literature that comes with the unit before you buy it, to make sure that you are getting an instrument that is highly accurate, preferably within 0.5 degrees Fahrenheit, either way. Less accurate equipment is not worth considering because it presents too many dangers for the lifeforms in the aquarium.

Many types of heaters are available. From the very inexpensive and highly inaccurate bayonet heater (usually imported and not intended for the reef tank), to the more expensive bayonet heaters from Germany (for example Ebo-Jaeger brand). Other types include flexible silicone cable heaters (dangerous in reef tanks because the cable can easily be ripped by rocks and some fish) and excellent quality American made bayonet heaters made, for instance, by Aquarium Systems.

Most hobbyists will require some form of heating, some time of the year. If possible use more than one heater. Let me clarify: if you need 100 watts of heat, use either four 25 watt units, or two 50 watt units. If you need 250 watt, use one 100 and three 50 watt heater. The reason for this recommendation is simple: because bayonet heaters can "stick" and possibly boil the tank if they do, more heaters protect you from a dangerous overheating of the aquarium. Small wattage units are less likely to heat the water to the point where it becomes dangerous, even if they stick.

Keep the temperature stable around 75-76 degrees. This will probably require some form of heating during the night, and maybe some form of cooling during the day, especially in areas where the daytime temperature runs very high, or if you are using lighting that is transmitting a lot of heat to the water and/or pumps that put of a lot of heat and transfer it to the water in the process of keeping cooler.

You must, of course, get the right kind of light for the reef aquarium (see a later chapter), but you must also make sure that only a minimal amount of heat is transmitted to the tank by such lights. Use either pendant type lighting, or make sure that the hood housing the lights is equipped with one or more fans that remove the hot air from inside the fixture, and thus reduce heat transfer to the water (companies such as Energy Savers offer a very wide choice of lighting sure to satisfy your needs). If yours does not have such a fan, muffin fans sold in electronics stores and often used for computers, can be used and retrofitted rather easily.

Pumps, too, can also be a great source of heat transfer, especially submersible pumps. Indeed, the latter use the surrounding water to cool down and protect their internal parts. Some brands of motors are notorious for transferring heat, even though they may be advertised as cool running. You should talk to other hobbyists to determine what their experience has been with individual brands. We tried an Iwaki 55RLT motor on one of our skimmers recently and, using a thermometer equipped with a special probe, measured a temperature that varied between 106 and 111 degrees Fahrenheit. Much too high of course. This does not mean that all such pumps will run that hot, but it is certainly food for thought, and reason for getting more information.

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