Lighting for non co2 tank

I am in the process of setting up a non co2 tank. The tank is a 20H. The NO light fixtures available for this size tank all have cheap plastic reflectors and the bulbs are only 18" long. I have such a fixture with 2 bulbs and even lining it with aluminum foil I could not get a par reading of even 30 at the substrate.

My plan is to raise the T5 fixture which is on the tank now to a height where the par readings are in the 50 - 60 range at the substrate. Will this work or am I going to algae hell ?

 

I had a gut feeling this was probably too much light. One thing I noticed with T5 lights is how quickly the intensity goes up as you move the par meter sensor up toward the surface. Since I will not be growing many of the traditional carpet plants the light levels at the substrate level may be less of an issue. Most of my plants will be several inches above the substrate.

I'll do some more testing and see how much higher I have to raise the lights to further reduce the intensity.

Thanks for your thoughts.

Henry