I actually have the Aqua UV57 watt myself.. And it actually on my system adds no heat at all(the combo of the pump and the unit). I was actually going it would, but not one little bit.
It could be because my system is in the basement, and it could also be the amount of flow I have going through it.. I'm using an ecoplus 1056 pump but that is because of my system volume.. I kept my runs short, and I'm estimating around 1000gph.. I am also tossing around the idea of going up to an ecoplus 1396(i believe that is the next size up).. I'm only using the uv for water clarify, so with that unit, I could definitely ruin more flow through it..
But you typically have to put quite a bit of flow through the Aqua UV units..
From note 5.. rip note 7