Yeah, I've just put an order in for 5 of them. Essentially it is a professional quality product designed for process control (manufacturing, industry, etc) that is now being made available with slightly cheaper components. It has two relays inside it - one that comes on when the thermometer detects cold temps, and one that comes on when the thermometer detects hot temps. You set the temps and the 'fudge range'. What I like is that it is also able to have the actual normal temperature calibrated/adjusted. I hate having 10 digital thermometers in the same area of the tank and they each have a different temp in a 2.5 degree celcius range from coldest to hotest reading.
my recommendations for wiring up:
Buy a short extension lead, cut it 2ft from the female end. Wire that short female bit into the heater relay output, and plug your heater into that (this will keep your heater in normal working order). Wire the long male end of the cut extension lead into the power input of the device. If you want to activate the cooling side of things, maybe also consider wiring the lights to turn OFF when the tanks get too hot as well (or turn on a airbubbler or a spray bar or turn off any internal power heads that make the water hotter)
As it is slowly coming into Winter down here in Australia I'll be using mine (when they arive) to keep the temperatures steady in my main tanks. 12 months ago I lost 5 hillstream loaches when i set the heater and walked away and the temperature hit 31 degrees in the tank. Then over the next 6 months I can work on making a diy chiller out of an old window airconditioner.
What I like about something like this thermostat controller is that you can set your heater to 28degrees c (or whatever that is in F) and then if the controller ever malfunctions then the heater shouldn't get any hotter than that - -- but in normal operation the controller will turn the heater on and off via a digital process to maintain the heat in the tank.
I gave my 6 otos some microwaved zuchini slices last night and this morning all 6 of them have the fattest bellies I've ever seen on them - the smallest of which was still very actively munching on the soft section even when I left home this morning. 2 of them are quite a lot 'rounder' than the rest, so I might have to consider adding some leafier plants in and removing the canister filter just in case I end up with some little fry (there are many online reports of oto fry, just google 'oto fry'). My canister filter seems too strong as sucks away any of the algae/vegie flake/spirulina mush that I pour in (as per your recommendation), so I might also add a little agar-agar and make small diy food jellies.
I see a couple that will hang out from time to time on the other side of the tank.
