It's been a while since I posted but...

Was curious if you're tryin to avoid algae(finally got it under control). Should I raise intensity or duration?

Depends. How much light do you have, and how long are you running it? Also, tank size, ferts, CO2?

For me intensity is important than duration. If you have the proper intensity, the plants will grow even for a minimal time the lights are on, which for me 7 hours is enough to avoid or encourage alage. If you don't have the proper intensity, the plants will not respond well even the lights are on for longer hours. Not sure though if the algae prefers that condition.

Intensity is more important than duration.
If lighting is too intense,then even short photo period could be too much.

The part that confuses me about this post is the word raise. If you are trying to avoid algae, I don't think that increasing the intensity or duration is likely a good idea.

Unless, of course, your plants are in poor health due to a lack of either of those. In which case, an increase would help avoid algae by giving you healthier plants.

Good point, although not usually the case. There is always so much going on in a tank, which is why I asked about the other parameters.