For you engineers here, is there a formula I can use to determine what size heater I would need to raise water temps in my indoor RAS tank? BTU's needed? Water temps stays in the mid 60's (it's in the basement), but I may want to raise it about 10 degrees for faster fish growth and more optimum biofilter performance -- if it's economically feasible.

The water in this circular stock tank is 324 gallons.

Too Late!

I found this:



Determining Heating Requirements for Electric Immersion Heaters

To determine the heating requirement of a tank, first obtain the following information:

1) Total cubic feet of tank. (Multiply the inside dimensions of the tank in feet - length x width x depth.)
2) Total gallons of water. Multiply by 7.48 the cubic feet of the tank occupied by water. (If the water is normally 6" below the top of the tank, allow for this when figuring.)
3) Average ambient (room) temperature at which tank will be used.
4) Temperature level at which water is to be held.
5) Heat-up time desired.

Losses due to agitation and ventilation should be considered in calculating total kW requirements. After this information is known, the following calculations can be made:

A x 1.0 x 8.35 x B = _______________
3412 x C

D x E = _______________

Add the results of both calculations. The total is the Kilowatt requirement of the tank.

A = Total gallons of solution. One liter = .264 gallons.
B = Difference from ambient temperature and desired water temperature in degrees F.
C = Desired heat-up time (hours).
D = Heat loss of tank. Refer to chart below.
E = Square feet of top of tank. Multiply length x width.

SURFACE LOSSES IN KILOWATTS FROM OPEN HOT WATER TANK (ºF)

75°


.01


80°


.02


85°


.03

Based on 70ºF ambient temperature.

http://www.process-technology.com/processtechnol/aquainfo.htm#Process

To ignore all that fancy engineerin', Cecil, 300 watts has no trouble raising the temperature of 100 gallons in my basement about 8 degrees, every day after I drop the temp by changing roughly 75% of the water.

Since you are recirculating rather than starting over with well water temps, 300 - 600 watts should be plenty for your application.

Thanks Theo!

Cecil:

If you need some heaters I have 3 or 4 300 watt heaters that I won't be using this Winter.

O.K. I may be interested. Just out of curiosity how much power do they use?

3 or 400 watts? They should nearly 100% efficiency, meaning power in=power out. jmo

Except for the waste heat.

I look at it as burning 3 or 4 100 watt light bulbs. (per heater)

And that, folks, is why Theo is a moderator.