This article was originally published in the September/October 1997 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.
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Home Energy Magazine Online September/October 1997
The Rage for AquariaResidential energy auditors often dismiss or overlook aquaria in their assessments. Yet nearly one in every 12 households owns at least one aquarium. Depending on the equipment used, the tanks can draw a surprisingly large load and occasionally qualify as the single largest end use in a home.
Most freshwater aquarium setups include fluorescent lighting, a filter, and an aerator. The three basic types of aquarium filters are:
Our prototypes' energy usage barely approached that of a microwave oven. Nevertheless, sometimes the loads can be much higher.
Some hobbyists go for a lush plant growth in their tanks. These densely planted tanks need extra lighting. A small tank will use 20 watts of lighting (approximately 2 watts per gallon), and the annual total energy consumption will range from 110 to 140 kWh. Medium tanks will require nearly 60 watts and will use 300 to 340 kWh per year. The lighting requirement of a large tank is more than 100 watts, and energy consumption will range from 570 to 650 kWh per year.Coral Reefer Madness? Reef hobbyists build tanks that simulate the conditions of a tropical coral reef. These are the largest, most complex of all the aquaria. They also generally consume the most energy.
The typical reef setup uses a tank and gravity-fed sump combination. After the water flows down to the sump, a powerful pump returns it to the main tank. Another pump pulls water through a protein skimmer, removing amino acids, lipids, phosphates, and other nutrients needed by algae. Reef hobbyists also like to use power heads, which they frequently control with a wavemaker. Because corals do best when water surges in different directions, the wavemaker turns power heads on and off to recreate turbulent reef conditions.
Reef tanks use an average of 6 watts of lighting per gallon, which, in combination with the pumps, frequently creates tank temperatures well above the tropical temperature of 75°F. As a result, the tanks generally need cooling rather than heating. Cooling is often achieved with fans located below the lights that blow air across the water increasing evaporation and cooling the tank. Sometimes, a small air conditioning unit called a chiller is attached to the tank. The fans are relatively inexpensive and are cheaper to operate than the chillers (chillers are rated at approximately 1,800 watts); they are thus the favored option among hobbyists.
During the summer, the fans may run all day long. In other months, they run only when the lights are on. Some reef hobbyists have also been known to run the house air conditioning unit to keep room temperatures low.
So how much energy does a reef tank use? We compared two prototype tanks, a 55-gallon and 180-gallon tank, using typical setups. We found that the 55 gallon tank used around 3,000 kWh per year, while the 180-gallon tank used over 6,000 kWh per year. To put these numbers in perspective, the energy used by the smaller tank was greater than the energy used by a typical home's central air conditioning system and lighting combined. Energy used by the larger tank was greater than the energy used by a typical home's central electric heating and refrigerator combined.
These numbers clearly indicate that auditors need to take careful stock of aquarium energy use. That's no fish story!
--Marla Sanchez and Alan MeierMarla Sanchez is a senior research associate at the Lawrence Berkeley National Laboratory in Berkeley, California.
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