Has anyone used one of these, A friend has one on his 5G hex and says the light is excellent and great for plant growth.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=260685119173&ssPageName=STRK:MEWAX:IT
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=260685119173&ssPageName=STRK:MEWAX:IT