Mostly malfunctioning problems. I've had to replace five ballast in the last year with one guy having to replace the same ballast twice. The latest ballast started making weird noises. That said, I've probably sold 20-25 of these units already, so the actual number of problems isn't extraordinarily bad, just nowhere near as good as I expect from a finished product.

I ended up sending one of the original 150W HQI bulbs that came with my 48" 150W Aqualight Pro unit as it was buzzing quite loud. I guess there is always a chance of receiving a lemmon product. I tried searching the net for any discussions about problems with 'any' of the Aqualight products - couldnt find any... Oh well, I feel better, I was thinking it would of been a more serious problem more frequently.

Heh, I've never had a problem with the 150 HQI bulbs or ballast though. Personally, I wish they'd just sell the combo units with no components (bulbs and ballast).