Ideal is dependent upon a lot of things. What works for some may not work for others. IMO
, 7-8 hours is a good start. I've had fantastic luck with a split photoperiod, running 3-4 on, 4 off, 4 on. That has worked very well for me to help keep algae at bay.
"What, exactly, is the internet? Basically it is a global network exchanging digitized data in such a way that any computer, anywhere, that is equipped with a device called a 'modem', can make a noise like a duck choking on a kazoo." - Dave Barry