Light intensity and duration effect on plants

[monty67]

Ok, so if you have way too much light and you cut the amount of time the plants get the light do you negatively affect their growing because the duration is lessened?

For now I am running my only lamp, twin TO5 on my twenty raised about 6 inches from the water. I'm only going about 7 or 8 hours otherwise I think i would be in algae hell. I will be lowering the amount of light so i can run them for 12 hours. But for now am i hurting the plants by cutting down the duration?

[Darkblade48]

Originally Posted by monty67

I will be lowering the amount of light so i can run them for 12 hours. But for now am i hurting the plants by cutting down the duration?

I am confused; you are going to lower the light intensity and increase duration, but then you say that you will be decreasing the duration?

[monty67]

Sorry, I should have been more clear,

right now i have running more intensity with less duration, I want to lower the intensity so can run the lights for 12 hours at a time.

is it all a wash or do the plants really need that 12 hours as opposed to a shorter time with more intense lighting?

[Darkblade48]

You can get away with 8 hours with high intensity lighting.

Conversely, having lower intensity lighting but for longer durations will do nothing but encourage algae.

[Gold Finger]

Yup. More light for less time discourages algae with no ill effect on plants even below 8 hours. However, if you have WAY too much light as you say you can cut intensity (say by blocking some % of the light with tape or window screen) and then you can extend to 12hours. Too much light is an easy fix. Too little light plus too long a photoperiod as an attempted fix just grows algae.