I agree that safety should always be a priority, and I am not suggesting that you abandon the UL listing. I would like to point out something about the UL listing. It simply means that UL has taken a product ( light fixture in this case) and tested it for safety and operation at it's intended use. That is the only use that product is listed for use as. Anybody that has taken a fixture apart and used pieces of it in a canopy, or purchased the retro kits for their system, does in fact have a non UL listed fixture.
The oddyssea fixtures use standard components. They have chosen not to submit samples to UL to tear apart and test.
With the one Oddyssea fixture I have, there have been more pros than cons.
Take a look at these guys too. Catalina Aquarium
I have this fixture in the 48" model and think it's a very nice fixture. Watch if you are not in a hurry, they go on sale from time to time.