Heater Sizing


A great deal of research has gone into heating for Aquaponics.  Where we live, we can have 40 degree swings in temperature.  Looking at all the options a mix of heating styles seems to be the best and probably the most costly at start up.  Most Aquaponics systems circulate water which makes it hard to control temperature.

If you are bringing water into your facility that must be heated, you can use an electric heater for all or just a portion of your heating. For instance, you may use solar, waste heat, or room heaters first and use thermostatically controlled electric heaters as the final temperature control.

To determine the approximate size heater to order, choose ONE of the three categories … then follow the calculation.

  1. Recirculating
    In a non-flowing system, heat is only lost to the surrounding air. The temperature difference between the air ambient and the water is the biggest factor. Also, the open area of the tank, the amount of agitation, and the heat loss through the tank walls should be considered. All external pipes, filters, pumps, etc. will further cool the water.For every 9°F (5°C) difference, there should be 4W of heat per gallon (3.8 liters) of water. Elevated, uninsulated tanks, with a large amount of surface agitation, could require as much as 12W per gallon per 9°F. For small glass aquaria, use 8 W per gallon per 9°F.                                                                                                                
  2. Temperature Raising Only
    Cool water is used to fill tanks and the water needs to be warmed before the fish are added. Time and ambient temperature will be considerations. For every 1,000 gallons (3,800 liters), 1,200 W (1.2 kw) is needed to raise the temperature 10°F (6°C) in 24 hours (this assumes ambient temp is the same as the water).
  3. Flow-Through Heating
    A flow-through system has cool water entering and warmed water leaving (this is very wasteful and expensive without heat exchangers). Determine the maximum gallons per minute that you expect and the greatest temperature difference.1,000 W (1 kW) will raise the temperature of 6 gallons of water (23 liters) one °F (.55°C) per minute.
    Example: 6 gpm with a 10° F difference = 10 kW.

Quick Heater Sizing Guide for Non-Flow Through Calculation
It’s difficult to simplify something that is complicated, but use this quick reference chart to estimate the size of an electric heater.

A tank with 1,000 gallons is in a room that will stay around 60°F, and you want the water temperature to be 87°F. If 4 W per gallon are needed for every 9°F, then: DT = 27°, 27 ÷ 9 = 3, 3 x 4 W = 12 W per gallon, 12 W x 1,000 gallons = 12,000 W. Assumes one large uninsulated uncovered fish tank plus one peripheral (such as a sand filter), and a pump with no extreme water/air interface (such as splash aerator or degassing tower). Minimize heater size and power use by insulating and covering.

Follow the chart to keep the water at desired temperature, but if a few degrees temperature loss is tolerable during brief periods of cold weather, use that temperature on the chart.TT74_chart_rgb