How long should I run a light that does not have a ramp up and down?

[Canned55]

Just for some background I am going to be setting up a small frag tank from a 20 gallon long. This tank will be limited in terms of livestock.
The light that I wanted to try out is one of the "black box's". I do not believe that this light is going to have any sort of ramp down.
All that the light is going to have is dimming functionality.

What my question is how long should I run it since there is going to be no ramp up or down.

(Here is the light that I will be using)

 

[Mr. Mojo Rising]

The ramp up and down is more for us than the fish, corals and fish don't care about ramping up and down. The only benefit of this feature is not frightening the fish with sudden turn on and off, but the fish will eventually get used to it anyway.

Go back 15 years and no one had ramp up and downs, just turn on and off. One of my tanks has a nicrew light with no ramp up and down, just turn it on and off.

 

[bobnicaragua]

Run them 8 - 10 hours.

 

[GARRIGA]

Lots we do today more for ourselves then the fish plus adding features differentiates products and sellers constantly looking for an edge.