actually its a closed system.
The top closes, and it uses convection to cool the pot.
but like WB is saying its not a very good unit.
It probably has a max heat capacity of around 100-150W, which is well within a single processor range, until you get into high overclocking quadcores.
Zalman offers an optional fan for the unit, and you can get that to boost your cooling potential.
As for waterblocks, if your set on using it, the only blocks i would recomend are the ones from zalman.
Possibly koolance might work because the base is nickle plated, and innovotek would also work since they dont have a cpu block thats copper.
I would avoid mixing a copper block in your reserator tho, and i would use a 50/50 mix of antifreeze + Distilled or a premix.
A newbie should not be mixing metals.... that will most definitely make you never want to watercool a computer ever again.