HI,
I have just built one and it successfully rooted 7 out of 7 clones, I kept the temp to 24 with an aquarium heater with the thermostat.
I had a timer on the pump doing 30min/30min.
I had the pump going 24/7 when the roots came out and I added 1/4 nutes then.
Either way I think the clones would have rooted with 24/7 or not, the plants seem to be really strong.
the only thing I was told to watch was the temps.
Ah also I didn't use any lights whatsoever, the cloner was near a south facing window but would never get direct sunlight. the light thing might depend on the strain though as mine is a strain that likes the outdoors I didn't want to stress it with lights.
cheers