Power

Reef AquariumReef Tanks Using Circulation PumpsTween Pump

Essential circulation is created by an in-tank powerhead, left; ever-changing currents are provided by the Osci-Wave, right, which rotates, sweeping its output 90 degrees back and forth.

tween two pumps to produce a pulsed flow simulating tidal currents. Alternatives include using a larger system pump and directing the return flow through various outlets to create turbulence. Submersible centrifugal water pumps may also be used for this purpose. Many public aquariums employ "dump buckets" to produce random surges, but this method may prove too messy for a home installation. As long as turbulence and good water movement are present, how this is achieved is important only in terms of the reliability of the equipment and its cost.

Temperature Control

Temperature control may require a heater or, more commonly, a chiller unit. Tropical marine organisms do best at temperatures within the range of about 70 to 80 de grees F, with the optimum being 75 degrees. The role of temperature in the maintenance of aquatic organisms is significant. The metabolic rate (the way in which the body obtains energy from foods) in fishes is highly dependent on temperature. Keeping coral reef fishes at the optimum temperature of 75 degrees results in better health, fewer disease problems, and longer life spans than if they are kept at higher temperatures.

To determine if heating or cooling will be needed for a particular aquarium installation, the best route is an empirical one. Place the tank in the desired location, fill it with water, and record the temperature over a period of time. If you're only at the planning and shopping stage, use a big plastic trash can or similar container with a capacity close to that of the tank you envision. Depending upon where you live and the temperature fluctuations you expect in the area where the tank is to be located, you should elect to make

7 j these observations when the ambient temperature is most likely to deviate significantly from the desired aquarium temperature of 75 degrees F. The use of central heating, air conditioning, fans, etc. will all affect not only the temperature of the aquarium but also the rate of water evaporation. Because of its weight and fragility, any aquarium, once in place and full of water, is an effort to relocate. It is therefore important to choose the location of the aquarium carefully. As simple a choice as placing the tank on an inside, rather than an outside, wall of the room made it possible for me to maintain the temperature of my first 10-gallon aquarium at 75 degrees. Perhaps the stable temperature contributed to my limited success in rearing the offspring of a female Dwarf Octopus (Octopus jouboni) that brooded a string of egg clusters in the aquarium shortly after I obtained her from a local shop (Tullock, 1980). In the long run, it is worth it to take actual temperature measurements in the proposed location of the tank under various conditions. The larger the tank, the more important this aspect

of planning will be. Heating and cooling water can be profligate of electricity and a significant cost issue, depending upon where you live. Probably the ideal location, and precisely where my next aquarium will be built, is in an enclosure away from the outside walls of the house. From the__

living space of the home, only a front or corner view of the ^^^^^^^^^^SSII^^^B^SBS^SnS^d I aquarium will be apparent. All of the equipment, hidden behind a wall, will nevertheless be easily accessible in a closet. 1 f one is willing to make the commitment, the sky's the limit with a large, built-in system.

An average temperature that departs significantly (say

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by 2 degrees) from the desired range will require artificial adjustment. Lighting systems and pumps produce heat. Submersible heaters are self-contained, adjustable, and com-

This additional heating should be taken into account in pletely waterproof; allow 3 watts per gallon of system water.

evaluating the temperature stability of the system. Especially for large systems that require hefty pumps and many 100-watt heater will raise the temperature of the tank 5 de-watts of artificial lighting, cooling the water by means of a grees in two hours, a 200-watt heater will simply raise the fluid chiller will be required

Self Contained Reef Aquariums

temperature of the water by the same amount in only one hour. Rapid changes in water temperature are not the rule in aquatic habitats. The high specific heat of water results in the moderation of temperatures. In fact, this is one reason the sump. (Many residents of northern states have timed why an aquatic habitat can be more biologically diverse than thermostats controlling their home heating in winter. If the adjacent terrestrial habitat.

If additional heat is required to maintain the temperature of the aquarium above 70 degrees F, select a good-quality heater, preferably of the submersible type, and install it in you are programming your furnace to run at 72-74 degrees

An aquarium chiller (also called a fluid chiller) oper-

during the day and then drop to 65 degrees or lower at ates in essentially the same manner as a refrigerator or air night, the aquarium will definitely require a heater to avoid conditioner. Refrigerant gas, commonly Freon, is com-

a daily temperature shift that will destabilize marine crea- pressed by an electrically driven compressor. This results in tures.) Allow about 3 watts of heating capacity per gallon the gas losing energy (its temperature goes down). The of water in the system. A 75-gallon system would normally compressed gas flows through a heat exchanger, where it have a 250-watt heater installed, since this is the heater size picks up heat from the surrounding medium, in this case nearest the required capacity. But it would be better to use water from the aquarium that is being pumped through the two 150-watt heaters for this setup, rather than one 250- exchanger. The gas carries heat back toward the compressor, watt. That way, if one heater fails, there will still be some but on the way it encounters an expansion valve, which al-

heating capacity. The likelihood of both heaters failing si- lows the pressure to drop suddenly. As the pressure drops, multaneously is small. There is no benefit in installing a the gas gives up heat to a radiator, which dispels the heat heater significantly larger than the required capacity. If a into the surrounding air with the aid of a fan. Although this is a relatively simple process to describe, building a refrigeration unit requires considerable precision in the machine shop.

A chiller does not "create cold." Rather, it removes heat. The rate at which a particular chiller removes heat determines its efficiency. Heat is measured in BTUs (British Thermal Units). One BTU is the amount of heat required to change the temperature of 1 pound of water by 1 degree Fahrenheit. The higher the BTU rating of the chiller, the faster it will lower the temperature of a tank of a given size. This means, in practice, that a chiller with a high BTU rating will keep the tank at a constant temperature with less use of electricity and less wear and tear on the compressor than will a chiller of lower BTU rating. Unfortunately, often a particular chiller's BTU rating can only be determined by actual use of the chiller on an aquarium, which is seldom practical if one is merely considering a purchase. The dealer or manufacturer may be of help in providing specifications.

There are some aspects of chiller design that even a novice can inspect. For example, the physical arrangement of the chiller components is important. The heat exchanger and compressor must be in a fixed position relative to each other. This means that chillers with a flexible connection between the exchanger and compressor — so-called "drop-in probe" types, are a poor choice. (If the exchanger, or "probe," is placed above the compressor, the exchanger will be starved for refrigerant gas; iflower than the compressor, the exchanger will be flooded, assuming they were designed to operate on the same level originally Additionally, many users have reported problems with corrosion of metal drop-in heat exchangers and their fittings.)

In addition, the choice of material for the heat exchanger is important. Remember that the purpose of the heat exchanger is to gather heat from the water. Heat-gathering is largely a function of surface area exposed to the water, thus as much exchanger surface as possible must be brought into contact with the water in a given period of time. Chillers using exchangers composed of the metal titanium, for example, generally have smaller, less efficient exchangers. This is because titanium is intrinsically expensive, difficult to machine, and a poor conductor of heat (similar to stainless steel). Titanium is used for marine tank chillers primarily because it is one of the few affordable metals that are impervious to seawater. (Gold or platinum would do, but both are highly impractical choices.) A satisfactory exchanger for marine tank use can be made of copper tubing sheathed with a plastic such as Teflon. This material is relatively cheap and is impervious to seawater. Also, copper is the best conductor of heat known (except for sterling silver, another impractical choice).

Aquarium and Fish Care Tactics

Aquarium and Fish Care Tactics

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