Large Aquariums Require More of Everything
My 8000-gallon aquarium is located outside near Seattle Washington, USA, just south of the 48th Parallel. The average temperature year around is 52.8 degrees Fahrenheit. See monthly averages, link
http://www.cityrating.com/citytemperature.asp?City=Seattle.
Electricity cost is $.0924 per KWH at present. This means a ¾ HP water pump drawing 10 Amps @ 120 Volts will consume about 1,200 watts per hour (10 times 120) or about 1.2 KW (1,200/1,000). The monthly cost of operating this pump works out to be 720 hours in a month times 1.2 KWH times $.0924 per KWH or about $79.83.
Heating my well-insulated 8,000-gallon aquarium requires about 3,000 watts per hour during the winter months. In the spring and Fall 1,500 watts per hour is sufficient and during the summer, no heating is required. The aquarium is covered with glass, which passes Radiant heat into the water. At nighttime, I cover the aquarium glass with Styrofoam panels. Using the above calculations my aquarium heating requirements during the winter are 3,000 watts or 3 KW per hour times $.0924 per KW times 720, which comes out to about $199.58 per month.
Another consideration is heating cold tap water during winter water changes. At present, the temperature of tap water is 42 degrees. Heating the new cold water requires about 20,000 watts per hour with a cold-water flow rate of 300 gallons per hour. I have mounted standard water tank heaters, two at 5,500 watts and two at 4,500 watts into my sump. These elements require 230-240 volts with 30 amp breakers. I drill holes in the sump or barrel for a standard 1-1/2 bulkhead fitting with 1-1/2 NPT threads on the flange side. The heaters have 1 NPT threads, therefore a 1-1/2 to 1 plastic bushing is required to mount the heater element inside the bulkhead fitting. The heater element has its own rubber gasket. Warning, if you use this setup, you cannot leave the heaters on after the water change is complete. I purchased water tank time clocks rated at 40 Amps, which automatically turn the heaters off if I should forget. John at
http://www.jehmco.com has temperature controllers for large heaters.
See pictures for further details about mounting water tank heaters.
