Have you though about a hood or canopy over the tank rather a fixture that sits on the top or hangs from the ceiling?
It's all personal preference but I did the hood to try to match in around the rest of the woodwork plus didn't want the light spilling out. I simply mounted some PFO MH mini-pendents and eventually a T5 retro kit. Could also try Lumenarc reflectors or appears you have some DIY skills build your own (
here).