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2.4 AQUARIUM SUBSTRATES:
The selection of the right reef tank substrate is an important decision. Then again, you will not need a lot of it. In reef tanks only very thin layers of substrate are used, and recommended. Putting too much substrate down directly on the bottom of the tank, can quickly lead to low oxygen levels in that same substrate, which in turn leads to anaerobic areas, and the appearance of hydrogen sulfide. The latter is a very noxious gas that quickly mixes with the water, lowers the dissolved oxygen level, and stresses the fish and other lifeforms, especially the ones in the lower parts of the tank.
Thick layers of substrate used to be the norm when used in conjunction with an undergravel filter. Since the latter is not part of the reef setup that we advocate, the amount of substrate used must be adjusted downwards considerably. We suggest that you do not place more than ¼ inch on the bottom of the tank, and only in those areas where you need to cover the glass or acrylic. You do not need to place substrate underneath the rocks. My own tank has no substrate at all! Not even a thin layer.
Undergravel filters, with their thick layers of calcareous rock, for example dolomite, crushed coral or coral rubble, served one main purpose: biological filtration, but they also served an accessory purpose: mechanical filtration. In reef tanks we want to avoid mixing different types of filtration. The reason for this is simple : by segregating the types of filtration, all can be present in their own right, and you can clean, replace, or do whatever needs to be done to them, without disturbing the others. Such is a major advantage, as it disturbs the chemical balance of the water chemistry much less, reduces the stress on the animal life, and results in a much better looking tank.
Dolomite, aragonite (unstable) and crushed or rubble coral, were also used to enhance the carbonate hardness of the water (see later in this book for more details). Carbonate hardness is very important to corals with exoskeletons (hard outside part), as the components of the carbonate hardness allow the corals to thrive, and even grow, providing the water the quality is up to par. Coralline algae require the calcium carbonate part of the carbonate hardness as well.
Both dolomite and crushed and rubble coral will increase the hardness for a short period of time. However, after they cover themselves with slime and other impurities, this beneficial action stops rapidly. Hobbyists then have to resort to the use of additives, e.g. liquids, powders, or tablets (we will cover this more in detail in a later part of the book).
Some hobbyists buy calcareous substrates in outlets other than pet stores. This may sound like a good idea. Often the material is cheaper. Unfortunately, the percentage of impurities in such materials is very high. This makes them unsuitable for use in reef tanks. Crushed oyster shell is an example of such a material.
When selecting a substrate, keep the type of animals that you plan to place in the tank in mind. Some need rocky substrates (live rock for instance, or similar types. They are sold under many different names), others require a smaller type (crushed or rubble coral). Moe (1989) gives a more complete description of the types of substrates that are found around reefs, and also some of the types required by the invertebrates you may keep. Advanced Reef Keeping II, my own book (published by Aardvark Press, late 1st quarter 1990), also deals with this subject in more detail.
German hobbyists prefer non calcareous substrates, especially since articles written by Preis (1987) advancing the theory that calcareous substrates may precipitate trace elements out of the water. This contradicts earlier statements by Wilkens (1976 and 1979) recommending the addition of lime water (kalkwasser) which increases the amount of dissolved and non-dissolved calcareous matter in the water.
My own experience has been that with regular water changes (see later) and the addition of trace elements on a routine basis, no such deficiency will occur, even at very high carbonate hardness levels. Since corals do better at these higher levels of carbonate hardness (Calcium and magnesium carbonates and bicarbonates as well as borate components), I recommend the use of live and similar rock in tanks, and the addition of KH generators and especially lime water, either manually, or by means of a dosing pump (explained later in this book).
It is important, when selecting the substrate and other rocks used in the tank, to keep in mind that you must be able to create strong circulation, also called current, throughout the entire tank. Such is important for the invertebrates, for the fish, and also for the quality of the water. Indeed, detritus needs to be moved around and into the mechanical filters; the invertebrates are accustomed to strong currents on the real reef; fish need strong water currents to keep them clean and healthy; and strong water movement inside the tank adds to the realism of the aquarium.
George Smit (1985) advocates the use of calcite and, as already indicated, Albert Thiel (1987) suggests the use of calcite in combination with the use of carbon dioxide, to increase the carbonate hardness of the water (see later chapters). Both, however, suggest that you do not keep thick layers of calcite on the bottom of the aquarium. Keep layers there as thin as you can. Your tank will benefit from it. The water quality will be improved. Levels of dissolved oxygen will be higher too.
Regardless of how much substrate you use, and which exact type you select, you must make it a point to clean it at least once a week, and more often if necessary. Accumulating dirt, dead algae, uneaten food, and so on, all contribute to the lowering of the water quality. As decay starts:
Those hobbyists presently using undergravel filter plates, who are considering leaving that undergravel in place, and adding a trickle filter to the system (see Converting to a trickle filter, later in this book, and also in my other book Small Reef Aquarium Basics), may want to read more on grain size, flow rates, and thickness of the layer, in Stephen Spotte's Seawater Aquariums, A Captive Environment, John Wiley Inter Science, NY, 1979.
2.5 OTHER BASIC EQUIPMENT NEEDED:
Besides the tank, a trickle filter, pump, the stand, and other items discussed in this book, other types of equipment will be necessary to keep a well balanced aquarium running successfully for long periods of time. Most of these are not the subject of this book. Moreover you are probably familiar with them anyway. Some of them include, amongst others:
If you are not familiar with them, refer to one of the many books that deals with basic aquarium keeping. TFH publishes several of them. Martin Moe's Marine Aquarium Handbook is also strongly recommended (Green Turtle Publications). Most of you probably have all that equipment already, especially if you have kept aquariums before.
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