Hi,
I dont think their bad units. I just dunked mine in the tank, and I didnt figure out what was causing the strange arcing and 'crreeaack' sound until 3 bulbs later. Then, I sent it into repair, and they do a good job at a very reasonable price, but the bulb fit too tight, and poof theirs another. I have two units, too, so its been a bear.
Paul