Question - what size aquariun heater, and should I get another Ranco to regulate the temp, or rely on the aquarium heater thermostat ?
Heaters are important for tropical set ups where the water temperature often needs to be higher than the ambient temperature of the room the aquarium is in. Many keepers of temperate/coldwater fish also keep heaters in their aquariums to ensure steady temperatures during winter when temperatures in the home can drop during the night when central heating is off. There are various different types of heater and different sizes available for different sized aquariums. The general rule of thumb is one watt per litre of water. For larger set ups it can be better to have two smaller heaters at either end of the aquarium to ensure even distribution of warmth.
Very popular in the public aquarium and aquaculture industry Aqua Logic's Delta Star inline water chillers feature water cooled condensers, making them ideal for installations with an existing freshwater supply. They use water to cool the condenser instead of air provided by a fan and motor. Their low heat emission, compact size, and quiet operation allow them to be used in tight spaces with minimal ventilation.
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What Size Heater is Needed for an Aquarium? | eHow
When selecting a heater for your setup, do not buy more power than you need. If the heater is too powerful for the size of the aquarium, the heater will cycle more often and will wear out sooner. It is possible, if unlikely, for the heater to fail where it is on continuously. The better heaters have a safety feature that will prevent overheating should the main thermostat fail. You should look for this feature in any heater that you buy. Turtle setups will normally include a basking area with a lamp. The lamp will provide some heating to the aquarium, but this should not be considered when selecting the heater. The heater should be sized to maintain the desired temperature when the lights are off at night. Note that the turtle must be able to get away from the light source as well to prevent being burned. To make it simple, get an adjustable, fully submersible heater that is the right wattage for the tank. Use a good thermometer to check the water temperature. A good rule of thumb is to use a heater with 4 to 5 Watts per gallon of aquarium size for small tanks and 3 to 4 Watts per gallon for larger tanks. Note that even if the aquarium is not filled, you should select a heater based on the aquarium size since most heat loss is through the top water surface. If you keep your house cool, you should size the heater using the higher wattage number. A perfect balance between price and functionality, the Hydor Heater Theo model earns its spot here as the fourth best aquarium heater.
Going back to the glass tubing style, the Hydor comes with a large, easy to read red dial top. The arrow points to the temperature setting. Simple, easy to use and more precise than knobs. Underneath the temperature setting dial is a large, multi layered rubber cover. While it is rare to be shocked by heaters, it can happen. These extra layers make the Hydor much safer in that sense.
Because the all black and silver color of this heater I have been able to use it in many tanks who don't want the heater to be a distraction while not adding on additional bodies of water such as a sump. Remember that you can set the heat before you put the heater in the tank, meaning you don't need to touch the dial after submerging and hiding the heater.
A small, but incredibly nice thing I noticed with the Hydor is the strength of the suction cups. While heaters, power head and submersible filters all can end up falling off the glass, the Hydor has exceptional suction strength.
The Hydor also comes in 7 different sizes, featuring the smallest size on this list. 25 watts to 400 accommodate all tanks within the range of 2 to 105 gallon tanks.