"Thomas Bartkus" wrote in message . ..
My concern would be the temperature swings over the course of an hour rather
than the course of a year! The term is hysteresis and typical cheap
thermostat mechanisms cause a lot of it. The heater doesn't come on until
the temperature is 4 degrees too low and then it doesn't quit until the
temperature is 4 degrees above the setpoint. All in all in an acceptable
range, perhaps, but how fast do temperatures swing on a tropical reef? How
fast in a 6 gal. nanoreef?

I don't know the answer to that question but I would like to!
I *suspect* that temperature swing (hysteresis!) in a nanoreef can be rather
extraodinary and stressful to the inhabitants. A serious thermostat control
may be of benefit.

Now you are touching slightly different subject...
Many of us use with great success a standard heater with embedded thermostate.
I am not sure if the hysteresis in such heater is that big (4'F) but even if,
it works great in many tanks. So yes, if you have nanoreef and your heater
has extraordinarly big hysteresis like 4F than I would be concerned...
Most systems I am familiar with the hystereris of a heater is less than 2F.

This will be similar hysteresis in an embedded thermostate inside your chiller.

I was rather talking about needing a chiller at all or living without one :=)