Lights on for how long ?

[BC564]

I run my lights for 6 hours a day....3pm - 9pm

[DiverDude]

ok...well I don't have any corals right now but I'm thinking of adding them in the future (hence the research on metal halides). Reading between the lines though, the general consensus is that ~15hrs a day my PC lighting is running now is not likely harming anything but it is probably wasteful.

OTOH, if I had MH, then 15hrs might, in fact, be bad.

[DiverDude]

Did more research and was having a lot of trouble finding 75W metal Halides (I have a centre brace in my 29 Gal tank and don't want a shadow from the brace so 2 lower wattage lights would be needed instead of a single lamp) and came across a section of the USHIO website that was quite informative:

http://www.ushio.com/products/petcare/aqualite.htm

In it, they state that MH lights should be on for at least 12 hrs a day...

No telling if that's a marketing ploy to use more lamps or if that's from a sound biological rational.