[Link: controlbyweb.com]I have just finished building and setting up two enclosures with the X-300 model that we will be installing.
If you just want an alarm for when the temperature of the water gets below a certain temp (you can adjust the set point) there is just some setup required.
If you want the alarm to go off when the air and water are below certain temperatures then you need the X-300 and there is some very basic scripts that you can write and load into the module.