As with most aquaria, the artificial life support is ultimately dependent upon electrical power. Were one to run out of kalkwasser, salt mix, or fish food, the aquarium could still survive for a long period, but in an ever degrading condition. If the aquarium is deprived of its source of electrical power however, its days (or hours) will be numbered. First, the loss of intense artificial light will cause all photosynthetic growth to cease. Higher on the food chain, herbivores requiring algaes will become at risk. The loss of light will bring ultimate and total devastation to the tank, but the loss of electrical power will have more immediate effects than this.
An aquarium will survive for days or weeks (depending upon the life forms it contains) without light. Remember, these animals regularly spend 8 to 12 hours in total darkness each night. Of greater concern during a power outage is temperature change and loss of circulation.
In some climates, a loss of power could result in the external aquarium environment reaching temperature extremes that are incompatible with aquarium life. How quickly this occurs depends on three factors: the volume of water in the aquarium, the temperature of the surrounding environment, and the heat transfer rate between this environment and the aquarium.
The greater the volume of water in the aquarium, the longer it will take for the water temperature to drift outside of its normally acceptable range. Heat exchange will be a function of the thermal coefficient of the materials used in the construction of the aquarium. Acrylic tanks will maintain their water temperatures much better than those made of glass. The amount of uncovered exposed water surface will play a large roll in heat transfer because it is totally uninsulated from the external environment and because in addition to convective heat transfer, evaporation can play a roll in the heat loss (though the latter can be good if the external environment is too hot).
My sumps have either glass lids (Jaubert sump and detritus filter) or floating polyethylene air-filled balls covering the surface. The polyethylene balls are a convenient way to minimize surface area in contact with the open air while allowing easy access to the sump for the introduction of liquids or additives. I maintain an open surface over the show tank to allow optimum light transmission from above, but I do have acrylic lids which can be put into place should that need arise.
In climates where temperatures fall below freezing in the winter, loss of electrical power can become quite serious. Even a well insulated home can have its internal temperature fall to 40 degrees Fahrenheit within 24 hours of a power failure in such climates. During the same 24-hour period a 200 gallon aquarium could drop in temperature by several degrees. This should not be surprising when one considered that the metal halide lights about a foot away from a show tank's surface can cause a 2 to 3 degree temperature rise in the space of eight hours.
On the other end of the spectrum, a loss of power during hot weather could cause temperatures to rise dangerously high for a long period. In general, many creatures will tolerate a gradual temperature rise of 15 degrees above the normal 70 to 80 degree "safe" temperature zone better than a 15 degree drop below that zone. Prolonged exposure to either extreme will kill many species.
In an unintentional experiment, a 10 gallon quarantine tank was heated to 90 degrees Fahrenheit for a period of 24 hours. Many life forms died, including green star polyps, nudibranchs, and macro algaes. Interestingly, all the red and blue legged hermit crabs survived, along with bristle worms, aiptasia anemones, and red bacteria. Tunicates and plankton seemed to die off, but the "seeds of life" remained and these ultimately returned without the introduction of new life. The quarantine tank did not contain any fish.
In another unintended experiment, a temperature controller reportedly stuck on a chiller and the aquarium it served fell to 57 degrees Fahrenheit. The owners of the tank noticed condensation on the outside of their tank. Immediately efforts were made to bring the temperature back into range, thereby limiting the losses to star polyps, a Catalina Goby, a jawfish, and a sailfin blenny. A week later, the same temperature controller failed and the tank got down to 51 degrees. The losses were a six line wrasse, all of the caulerpa, xenia, cauliflower leather coral, about 20 percent of the mushroom colonies, and the coralline algae turned grayish white. All hermit crabs and snails seemed to survive, but the elegance coral withdrew and did not do well for weeks.
What these two examples indicate is that green star polyps die with brief (less than 24 hour) temperature extremes either above the "safe" zone, or below. On the other hand, hermit crabs can take enormous temperature abuse at either extreme and survive. Also to be noted is that a gradual 20 degree dip in temperature will kill some things, but not all. Whereas a there is a point below which few things survive (in this case a 25 degree dip) even when cooled at the same rate.
To maintain temperature in the basement "Aquarium Command Center" and reduce introduction of airborne dust from the adjacent basement shop, I have installed vertical strips of overlapping black strips of plastic (made from sliced up carpet runner) to cover the entrance, thereby inhibiting air flow while allowing easy passage of people even when their hand are full.
Typically loss of light and temperature regulation are processes that will lead to the death of an aquarium system over a period of days or weeks. There is another manifestation of power loss which is the most devastating and quickest acting. It is loss circulation. When the circulation pumps are shut down, oxygen distribution is forced to take place only by diffusion from the surface. This is a slow process, and depending on the oxygen uptake of the life forms in the tank, it may be depleted faster than it can be replenished. Mobile life forms may be able to survive for a period at the water-air interface at the surface, but sessile organisms such as corals and worms will suffocate. This will be accelerated in some corals by the inability to shed mucous coverings due to the lack of physical water motion.
Without circulation, oxygen will be quickly depleted and regions of stagnation will go anoxic. As organisms (both microscopic and macroscopic) begin to die, anaerobic bacteria will begin to reduce the dead organic material and form hydrogen sulfide. This and other chemicals will reach toxic levels.
A combined lack of circulation, light, and out-of-range temperature variation will decimate a reef tank within 72 hours and can result in the death of many delicate species in as little as 12 hours. An investment of thousands of dollars can be lost right before your eyes while you stand by helplessly-- or you can do something...
In temporary power outages (up to four hours), one can probably do nothing and get away with it. If a longer outage is predicted, a battery-operated air stone may be employed in an attempt to keep the tank from going anoxic. Bear in mind that without circulation, sumps may develop hydrogen sulfide even though air is being applied to the show tank by means of an air stone. When the power is eventually restored, the stagnant water in the sumps will be pumped into the show tank with ill effect.
Also small battery-operated air stone pumps such as those designed to keep bait fish alive in a bucket, may not have enough power to drive air through an air stone submerged in a 30-inch deep show tank due to the hydrostatic back pressure. Another alternative is to get a small 12 volt inverter which can transform 12 VDC power (car or motor cycle battery) into 150 watts of 60 Hz AC power. One can then run a commercial plug-in-the-wall air pump which will easily drive a deeply-submerged air stone.
What if you live out in the country and can expect significant delays in getting power restored, or what about the infrequent ice storm, hurricane, earthquake, or nuclear war that may knock out your power for over a week? Well it becomes one of those 'pay now or pay later' decisions. One can assume that an extended power outage will never happen and accept thousands of dollars of loss and heartache when it does (i.e., pay later to reestablish the tank or simply get out of the hobby), or you can be proactive and buy a generator (pay a thousand dollars now) so that you can laugh in the face of adversity, confidently knowing that your tank has cheated death yet one more time.
Type "A" personalities will certainly want their own generator. I purchased an 8 KW generator that has the capacity to not only run all of my aquarium systems, but also runs the household life support systems such as the television and microwave oven (actually it also runs lights, heat, refrigerator, and the well pump).
Since I use propane to heat my home and to cook, I chose a multifuel generator that can run with propane. A buried 500 gallon propane tank supplies not only the household heat and cooking functions, but also the generator when it is needed. The generator consumes about 1.5 gallons of propane per hour under an average load. With a full 500 gallon tank, I could generate power to the house and aquarium for almost 14 days (note that storing an equivalent amount of gasoline to run a generator in emergencies is problematic in that gasoline loses its most volatile constituents in time unless special measures are taken to chemically stabilize it).
In reality, power can be rationed during an emergency, using it to provide light for a few hours at night, and to run the well pump periodically. Similarly, the aquarium can be run for periods, and allowed to "coast" in between.
Since my show tank is in the family room, its light is more than adequate to illuminate the room at night. By scheduling water use and heater operation, the generator could be operated during extreme winter conditions (worst case scenario in the Atlanta, Georgia area) for only eight hours per evening while maintaining reasonable living conditions both inside the house and inside the entire aquarium system. Therefore were an extended power outage to occur, both my family and the aquarium could survive reasonably with power rationing for three and a half months (104 days)! Chances are, when the power goes out my propane tank will not have 500 gallons in it, but then again, I will probably be worrying about more than television and my aquarium were there to be a disaster sufficient to knock out power for more than three months!
Here is how I have configured the generator. It is supplied with propane from an underground 500 gallon tank via a pressure-reducing regulator and a cutoff valve. The output from the generator is 220 VAC, 60 Hz split into two 100 VAC phases having a combined generating capacity of 8 kilowatts. These two phases are brought to a red receptacle panel which allows either commercial power or generator power to be supplied to selected circuits. Circuits such as the well pump, downstairs furnace, certain room lights and receptacles, the kitchen, and of course the aquarium (which is on one 20 A breaker) have been moved into their own breaker box.
If Phase 1 and Phase 2 plugs are both manually plugged into the lower commercial power receptacles on the red receptacle panel (pictured to the left), then the selected house and aquarium circuits derive their power from the commercial power grid. If these plugs are manually placed in the upper generator receptacles, then that becomes the source instead. The generator is always physically separate from the commercial power so there is never any danger of having the commercial service restored with the generator connected to the commercial line.
Four electrofluorescent panels indicate which phases are active. In the Figure to the left, the lower panels are illuminated, indicating that Phase 1 and 2 of the commercial power are available, and both generator phases are inactive. A voltmeter above the receptacles shows the voltage being supplied by either phase (switchable) of the selected source. Ammeters (upper right corner of red receptacle box) allow the user to keep the current draw balanced on each phase by switching Phase 1 or Phase 2 loads in or out of the circuit. In practice, some thought has gone into the selection of which appliances (loads) are placed on each of the two phases to keep the current in the phases balanced under typical conditions. The upper gray breaker box (shown with the door open in the Figure) houses the breakers for the selected house circuits, heater, well pump, and the aquarium.
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