Yes, there is a large fan attached to the radiator (from behind, so its not shown in the picture). It is the same fan that I toggle to control the temperatures. It has the added bonus of moving humidified air around the tank to avoid stagnation.
The circuit also controls a system to fill the humidifier and water my plants. There are water level sensors and humidity sensors that detect when things need to be turned on. Unfortunately, the watering pump broke (turns out it wasn't submersible). I'm waiting on a new one, but again all of this needs to wait a few weeks when I'll have more time :P .