PAR vs Intensity question

[EEE1986]

Hello,

I am setting up a UNS60A reef tank (20 gallons) and am currently in the process of cycling. I recently purchased the Danoplus PAR meter and used it today to try to dial in my lighting, but I am confused about the relationship between light intensity and PAR.

I am currently running a Gen 4 XR15 suspended approximately 13.5" above the tank. I plan to keep a predominantly LPS/soft coral tank and am aiming for roughly 50–150 PAR. I am also trying to keep the light high enough that it doesn't interfere with routine maintenance, so I am happy with the current mounting height.

The issue is that my PAR readings were higher than I wanted—roughly 100–180 PAR after applying the correction factor of +35 based on this YouTube test:

I assumed that simply lowering the intensity in the Mobius app would allow me to bring the PAR down into my desired range. However, I found that the PAR readings remained more or less the same when changing the intensity from 25% all the way up to 100%.

This has left me wondering if I'm misunderstanding something fundamental. Is it possible that:

1. The PAR meter isn't reading correctly
2. There is an issue with the XR15
3. PAR doesn't scale linearly with the intensity setting in Mobius

Any insight into what might be going on here would be greatly appreciated!

 

[BeanAnimal]

I would return the PAR meter. Place your corals and ramp the light up until you and the corals are happy over several weeks.

I have no idea where your desired PAR target came from or where those people got it or how it correlates to the spectrum you are running or the error in reading, meter differences or anything else. It is a feel good tool and metric.


That fixture will grow coral just fine.
Set the height so that the spread isn't flooding onto the floor.
Set the spectrum to be pleasing to you.
Start at lower intensity and ramp up over a few weeks.

You will get an idea of what works well.

From there start new coral at the bottom and move it up to its final location over days or a week or so.

 

[Tangdora]

Par should be increasing with intensity. Would check you Möbius setting. First make sure the current time is between your peek interval range. Also there are two ways to control intensity. The overall intensity slider. Or controlling each channel individually if you set the over all to 100 you can still be running at 25 if all your individual spectrums are all still set to 25 % each for example